Until recently I've been using Magix Movie Edit but my current version doesn't support mp4 video codec.
The latest one does but I've been looking around as well.
VideoLan has just launched their first edition of VLMC (pre-alpha) - same guys who brought us the legendary VLC player.
the 1st version is pre-release and missing some functions - I can hardly WAIT to see the final product.
Perhaps you can give it a go
http://trac.videolan.org/vlmc/