It would be nice to see the inclusion of the Sparkle framework (http://sparkle.andymatuschak.org/) for self-updating within the next update. Therefore future updates will be announced automatically by GrandPerspective.
I'd also like it if the app sent out a Growl notification (http://growl.info/) when it finished reading a folder or volume. Larger folders or volumes take long enough to read that us users go off and do other tasks while it's reading the drive and may not see that it has completed reading right away. A Growl notification would assist in that.