This firmware fixes a problem that was introduced some time after 220 and was present in 349. When playing tracks from MP3Tunes or the Media-Player, switching to standby and then back-on made the radio go straight to the last played radio station, and not back into media-player. 400 switches back on in media player mode so you can simply press pause to resume at the track that was playing before the unit was put into standby. Note that the offical latest firmware for the Logik IR100 was possibly slightly better at this because it would resume playing the last track without any button presses.
There are probably other fixes too (please insert on this page) 8-) (Hovis)