Another vote for grouping groups as many levels as we want! Grouping is my favorite feature in 8 but I can't believe it goes one level. After that it's back to bussing like we did in previous versions.
Waveform view for collapsed group tracks. Some kind of rough view of what the audio is to help with editing of collapsed group tracks.
Rendering tracks out could use a little more control than all tracks either mono or stereo. At the moment, the fastest workflow I have is rendering all tracks as stereo and manually dropping the ones that don't need to be stereo into audition or soundtrack pro to batch convert to mono. Or doing a pass of stereo and a pass of mono if I only have a few busses. A simple list with check boxes to enable which track to be rendered and another for mono/stereo.
A single key toggle for seeing automation like in Logic. That one feature (and space designer) make Logic better/faster for mixing many times.
Of course with automation toggling and better grouping, I won't need to bounce out to Logic and PT as often for mixing more complicated stuff!