I think its the least used system utility. Most users arent even aware that such a utility exists and what it can do to improve performance. Perhaps 'light' users may not find a difference, but anyone who uses the PC substantially will notice a good improvement in keeping the drives free from fragmentation. I recently helped a friend cleanout a drive that was choked and entirely red with fragments, he hasnt run the utility for months (after all the music movie downloads) and complains that it behaves as if its afflicted with some psychomotor disease.