Would be awesome if the lag time between when you hit spacebar and when music actually plays could be reduced. Ableton live responds much quicker. There is also lag time when you drop new tracks, if this could be minimize somehow it would be awesome. so you can add instruments etc. and not have the whole playback interrupted while in a session with other people listening/writing to the track.
Thats called the gapless audio engine. There is a thread already open with 114 posts right at the beginning of the FR forum.