I keep it simple (thus why I was prone to try SiB) I use Gstreamer for everything unless it flat out doesnt work and then I try MPlayer.

For me Gstreamer plays my H264/AAC files way better than MPlayer, even my medium quality encodes tend to lag a bit and get out of sync on MPlayer. So its just a backup to cover the odd job files like MPEG2 that Gstreamer wont play.

At some point I think the extra codec pack will have it so that one player handles everything without need to pick one.