Hi have a Galaxy S2, I can found only a bad thing in it: bluetooth audio quality.
I have done some search and I'm sure that GS2 (like most other smartphones) uses SBC codec to send data over bluetooth.
The problem with SBC is that it reconvert your compressed files, such as MP3 or AAC, before sent them over bluetooth, so the final quality is terrible.
You can improve a little the quality increase the bitpool (use an highest bitrate for the conversion) but sound quality will never reach Directly MP3 transfer without conversion, for example connecting an usb stick to your stereo.
But there are a lot of discussion about ad2p sound quality on xda, so I think that you already know that.
I think that create mp3 codec to work with GS2 is hard and difficult, but I have found that Blueplayer for Windows mobile and Motorola with Droid X/ Droid 2 use A2DP Mp3 direct stream, in the specific motorola enabling the option "enhanced stereo" in bluetooth menu (absent in SGS2):
So my question is: is possible to make a port of blueplayer or motorola bluetooth stack for Samsung Galaxy S2? I think this is the only way to improve bad bluetooth audio quality on GS2.