The things I would like to see improvements in:
1. The screensaver scanner. It would be nice to skin the progress box nicely, plus have more options, such as: Hide activity box; Stop box from moving around;
2. Inactivity scanner. Norton has this where if the computer is inactive for long enough, it just starts scanning in the background.
Other things I have seen other people already suggest that I second:
1. Make installer skin match that of the main application.
2. Small popup for scanning USB thumb drives when inserted. Nothing too intrusive though, I like how KAV 2011 does it, small window in the corner.