I like it a lot. I had a moto mpx200 which was also a smartphone (no bluetooth). I really miss the size of that phone and the clam shell. The Treo is bigger and not as convenient to carry, but I've already gotten used to it. I prefer/need a phone that is also a PDA, and the Treo with the Palm OS I think is much better than the mpx in that regard. The Treo is very easy to use and navigate. The keyboard, although tiny, is really nice for entering info, particularly if you use the messaging, email and web functions. The moto may have had a little better sound quality, I haven't used the Treo enough to make that comparison yet.
As for the wireless headset, I don't know yet. I'm waiting for a Plantronics headset that was ordered. I do know that the bluetooth in the GX works great!! :)