I'm using an Alpine CDA-9886 head unit with the KCE-350BT bluetooth adapter. The Pre paired with it effortlessly and is working fine for inbound and outbound calls. Unlike my Treo 700p, the pairing has never failed to establish or required a manual reconnection.
Dialed Calls, Received Calls and Missed Calls synced with the unit, but the Phone Book gets stuck at Updating if I try to go into it; probably because I have 1504 contacts in my Exchange profile alone, plus whatever contacts came over from Facebook and Gmail.
The A2DP/AVRCP profiles work brilliantly. I leave the Alpine set to the Bluetooth Audio source and the Music (Remix) card open on the Pre, then when I start the car the Pre connects after a few seconds (the Alpine will show No Unit at first followed by BT Audio) and two presses of Play/Pause on the Alpine (not sure why it takes two) restarts the music from where it left off the last time. Way better than the Softick Audio Gateway experience on the 700p.
The outbound phone quality (i.e. what the person on the other end hears) is terrible, but I blame that squarely on the KCE-350BT and its microphone, as people had the same complaint with it and my Treo 700p while my Motorola T505 had good outbound quality with either device. Alpine's latest BT adapters now license technology from Parrot, so hopefully their newer ones are better than this...
Edit: Okay, since posting this I decided to give the phone book in the Alpine one more chance at updating. I left it for an hour or so while I had breakfast and when I came back the entire phonebook, from Abe to Zeeshan, was in there. Wow! Downside, when I started the car and the power to the Alpine cycled, I hit its Phone button to try and originate a call and it was back at Updating again, which lasted the whole 15 minute drive to the office until I shut the car off. You can't control the unit (volume, play/pause or track skip, it just keeps playing what was playing) while it says Updating, so the stereo was a fancy and annoying boat anchor for the whole trip. Bottom line, KCE-350BT +
Prē works well for bluetooth audio; okay for receiving calls and calls originated on the phone; but don't try to originate a call from the head unit if you have a lot of contacts on your
Prē. This does not play well with the new Ontario handsfree law that kicks in two weeks from now, where just getting caught dialing your phone can net a hefty fine. Time to mount the Touchstone on my centre console as originally planned...