I don't know whether these had been mentioned before but I would like to suggest 3 improvements:
1) To add the feature to move a large folder (game folder etc) to the end of the drive. Currently we can only move selected large files.
2) To remember the panel sizes so that we don't need to resize them every time.
3) To display the color legend, maybe besides the pie chart diagram below so that we don't need to go inside to check again and again. Just can't remember those. Nowadays everybody's got a big screen.