Share your experience!
I bought my car audio severel years ago but I´ve had never problems to connect my also old iPhone 3G to the caraudio (MEX-BT2500) over bluetooth. Last year I bought a xperia sola and the problem appears that there will no audio-connecting over bluetooth to the MEX. But for some seconds the MEX shows both connections, telephone and audio, then the audio breaks. My question: is there a possibility to use my xperia with this car audio system over bluetooth? Do I need a special app or so? Or is there an firmware upgrade available on the MEX? I´m wondering about this^^
[UPDATE]
Ok, after a little investigating I found the function to initiate a bt-connection manually from the caraudio. Simply select "BT AUDIO" and press "6". That´s all. But, during playback it sounds with many clicks and mushes. Could this a problem with the caraudio or with the mobile? Maybe the bt-signal is not strong enough to reach the MEX? Or something completely different? 
[UPDATE]
Regarding the sound problems over bt to the caraudio I rekognized same problems with the music player in offline mode. After installing another audio player app from the playstore this problem could be solved. But first I have to test it on my car audio. But for now I allocate some performance problems with the original Sony apps by the ICS. After changing the original camera app by another, the cam is very faster than with the older app. In another discussion I read how to speed up performance by deactivating some of the "special" gimmics like live backgrounds, lower speed for the gui animations, the nfc funktion and the glove mode. So I´m looking now which apps are more suitable for the low cpu performance of the sola (but I´m wondering about this 1GHz dual-core cpu and it´s performance with ICS I expect more power^^). Could be a good idea to build a list of suitable apps for the sola with ICS for the next time...I do.
The phone has a 1GHz dual-core CPU but when you run an app in ICS it requries more RAM then it does in GB. If you find apps that uses less RAM they will probably run faster.
Regarding the problem you've had with the car it's hard to say what's wrong but if it works with other phones i recommend that you at least test your Xperia sola with a Sony headset to make sure there's nothing wrong with your phone.