It would be great if it where possible to re-arrange the order of the slices in the "slices" panel.
Now the order of slices is locked to the time when the slice was created it seems. The slice created first is always on top and the slice last created is always in the bottom. It would be easier to maintain good order in the list and easier to find your slices if you could re-order the list yourself.
Also, I think this has been mentioned before... But being able to duplicate a slice (same size and export properties) would be nice. Also, being able to use arrow keys to go up and down the slice panel would be convenient.