First impressions:
Motorola seem to have their finger on the 'cool' pulse at the moment and have been producing some very sexy looking devices and the HT820 is definately in the same league. They come in a nice looking semi-hard case, so you could shove them in a bag and wouldn't have to worry about them getting busted up. The accessories included is an AC charger (hooking into a miniUSB port on the right ear cup), a 3.5mm audio jack to connect the headphones to non-bluetooth enabled devices and of course the quick start guide and full manual. All of these things fit snuggly inside the case if you know how to pack it properly.

The build quality of these headphones is top notch. They're sexy (especially with the pulsing blue "M"s on each of the ear cups), they're comfy and they feel solid yet light on the head. It has 6 buttons. Volume up and volume down are located on the top of the left ear cup and track forward and backward on top of the right cup. The left ear cup also has the "Multi-Function Button" which turns the headphones on and off, sets the device into pairing mode, answers and hangs up phone calls, redials and puts callers on hold. The right ear cup button starts, stops and pauses music as well as doing a few other things (such as conference call connection) if you use the Headset profile.

It supports A2DP (Advanced Audio Distribution Profile), Headset and Hands-free Bluetooth profiles. If your device only supports the Hands-free profile you won't be able to use them as wireless headphones, but will still be able to use them as a Bluetooth headset for phone calls and pipe audio through them via the 3.5mm audio cable. As far as I can tell the 3.5mm audio cable doesn't have the ability to carry the microphone signal, so they won't act as a hands-free wired kit. I'm assuming the Headset profile also only offers limited audio quality, not having the ability to test the Headset profile I can't give an accurate comparrison, however having heard music from other devices in Headset profile through my Jabra BT800 headset the quality isn't too bad, a bit like FM radio really.

I haven't had the headphones long enough to test Motorola's battery claims, but they reckon you get 14 hours of audio playback, 17 hours of phone time and 500 hours of stand-by. Motorola also tell me that the battery takes two hours to fully charge. The AC charger is slightly annoying as the orientation of the plug means that it needs to be on the very right of a bank of plugs or otherwise you'll lose the use of the plug immediately to the right of the adaptor (think "stupid sideways Nokia phone chargers" and you and I will be on the same page). I will give it some extra points however as it has both Australian and what I assume is American style interchangeable heads so that you don't need to buy a converter if you go over there.
         

Performace and Tests:
The test platform I used was an o2 XDA IIs running Windows Mobile 2003 Second Edition. o2 Asia 1.40 WWE ROM with Broadcom Bluetooth stack v1.0.0.3900 with the I-mate PDA2k update for BT v1.0.0.3500 which adds A2DP and keyboard profiles to the stack (For this update visit the XDA-Developers WIKI). For all those that arn't aware the o2 XDA IIs has a very bad track record with Bluetooth causing most Bluetooth headsets not to work properly, poor range causing "line-of-sight" only connections, static and a bunch of other problems. So if anything I say here doesn't sound favourable, there's a good chance it's caused by the PDA rather than the headphones.

I have no idea if what I did to setup my headphones was the recommended way as I never read the manual (manuals are for school girls ) but never-the-less here are the steps I used.

Firstly I reset my device and then put the headphones in pairing mode (by simply holding down the Multi-Function Button for 6 seconds) and then paired it in a hands-free profile. Then I turned the headphones off, put them in pairing mode again and paired it with the A2DP profile.

Once this was done I was able to pipe all audio through to the headphones and, when a phone call came through, it'd switch on the hands-free profile (if it wasn't already on) and it'd act as a Bluetooth headset. The microphone is hidden in the right speaker and uses a digital signal processor (DSP) to clear up your voice for the other person. The audio quality in-call is great and you come through clearly thanks to the DSP. In the test calls I made it was reported that the HT820 doesn't have the "harsh" sound which is common on the audio coming from the Jabra BT800's DSP. The range is excelent and clothes don't cause static unlike so many other Bluetooth headsets (XDA IIs owners take note that this is one of the few headsets around that will work well with your device).

Because the XDA IIs does not support the Headset profile (instead it uses the Hands-free profile) if you're using the headphones to play muic when the call comes in, you'll have to manually stop the music before answering the call, the audio from the phone call and MP3 will both be garbled until you do.

Let me say, the audio quality is excellent. The range is good except if there's a substantial object in the way such as a body or a wall then the audio will become interrupted. They work through clothes fine, so there's no problem with having your device in your pants and, with line-of-sight, they've got a range of about 6 or 7 metres. I tested them with some very high quality MP3s (320Kbps) that I was familiar with and I compared with the headphones connected via the 3.5mm audio cable. I consider myself somewhat of an audio buff and I had to swap back and forth between them quite a number of times to tell the differences. The main difference is that the headphones are louder when plugged into the cable. This isn't a problem for anyone that isn't trying to send themselves deaf. The volume is as loud as I'd want to listen to music to any length of time. Wirelessly, they tend to favour (oh so slightly) bass sounds which can be corrected if you don't like bass with the graphic equalizer in The Core Pocket Media Player (TCPMP). Other than that I can't tell any quality loss, though if you have invested in some serious quality wired headphones, you may be able to hear some loss.

The HT820s can pair with up to 8 different devices and as far as switching between them goes, I assume it's just a matter of enabling the BT link from the device. Not as cool as the "Press a button and it'll switch" which the Blueant X3 Micro Bluetooth Headset has but is still very useable. To be perfectly honest I can't think of a time where I'd actually need to use that feature except for one case where you would be piping through music from laptop and receive an incoming call from the PDA/phone. In this case, as far as I can tell, it'll still cut out the A2DP link and establish the hands-free/headset profile on your PDA for the call. Or it'll have them both active and you'll have to disable the audio manually by pressing the right speaker cup button. The reason I figure this is because the headphones will allow my PDA to simultaneously connect via both A2DP and Hands-free, so I don't see any reason why it wouldn't accept these streams from different devices.


Problems:
One disappointment with the headphones is that it seems to interfere with MS Voice Command. This is probably because the XDA IIs doesn't support Headset Bluetooth profile, however it is still very annoying. The device mic is still used to detect your voice and somehow it seems to just be... deaf. You've got to speak louder and slower for some reason (I always have Microphone AGC disabled). Also, the audio from the voice is piped through the headphones for the first 0.5 of a second and then it just cuts out... It still seems to be "listening" for your responses, but you won't know when to reply unless you've used it a lot or you wait to see the speaker icon.
Example:

Me - Play Music
"Try ag..."
Me (Louder) - PLAY MUSIC
"What do y..."
Me - ARTIST
"Which ar..."

Me - Greenday
...
Me - GREENDAY!


Another gripe I have (it's probably more to do with WM2003SE than anything else) is that the A2DP link is disconnected when the PDA goes into standby mode (for me that's after 3 minutes of not playing with the PDA, even though there's MP3s playing) causing all music to cease and when you power-on the PDA the connection remains severed and the PDA starts blasting out music from it's build-in speaker. Once this happens, you have to go into Bluetooth Manager, disconnect the A2DP connection and reconnect it to re-establish the audio connection. Hands-free still remains connected no matter what. This is contrary to a wired headset pumping out music and every other Bluetooth profile and is quite annoying. Having said that, there should be an option in TCPMP to keep the device active, but if there is, I've yet to find it. The only remedy to this is to use the dreaded Windows Media Player 10 for Pocket PC when I'm not going to be actively using my PDA... *Shudder*