Ive used it and my only issue is that I can't get the car to recognize folder structure. I had all my songs in folders separated by artist and album name, etc... The car would only recognize the songs if they were saved without any folders.
Use an 8 gig SD (Sandisk) card. I copied my iTunes library via Double-Twist. Everything works as it should: Can call up by artist, genre, playlist, etc. Maybe i don't have that many tunes, but I have never had a problem with indexing as some others have had, BTW.