Sony Ericsson phones work great with Macs, don't think otherwise. Sony != SE.
The T809's music player software is quite basic and you can't do anything else with the phone while the music is playing. Speakers are loud, earphones are OK, but the proprietary plug sucks. Overall its a great phone, and only go for the Moto if you aren't swayed by the T809's looks and rich features.
The UI is OK (Speaking from the perspective of a former SE owner and current WM5 user) and the camera is great. It just looks better than many other phones, V360 included.