Currently if I set my DAP to encode to 128bps mp3 for example, this works fine for ogg files but not higher bitrate mp3s: banshee just copies them to the DAP without re-encoding.

This is unfortunate because on many cheap players you can't really tell 128 from 320 mp3 but the 320 version takes much more space.

So please add the option (perhaps even hidden gconf) to also re-encode to a lower quality version of the same filetype. Users with cheap =< 512mb players (which seem to be quite common still) will like this option.