Ok - Just updated to 5.5 on my GPA.
Seems to be fine, all I can say is wait. It seems to restart a few times, one of which does take a long time (looks like its doing FA, guessing its writing to flash or crc checking etc), eventually it said update complete etc tho..
Results:
My iPhone 3GS 32GB running iOS 4.0 with videos on it that had the initial problem of playing for 3 seconds then cutting to radio seems to be resolved..
My iPhone 4 32GB seems to be running ok too - no issues to report (have no videos on my iPhone 4)
My iPad - Not tested, cant be fooked as i dont see the point
One but that i *think* is squashed, is that after turning the engine off and leaving the iPhone plugged in, I can now brows through artists/playlists etc without having to disconnect/re-connect phone...
Time will tell how good this update is im guessing....