Actually, it is landfill and pollution issues more than anything that keep me from upgrading. PC manufacture is a dirty industry and I like to make my machines go as long as possible. Now that LCDs are cheap, I ask myself which is better - to keep running the power hog CRT and use up all that electricity, or to buy something new, which uses a lot of energy and creates a lot of pollution in the manufacturing process, not to mention disposal of the old monitor. I don't know whether pageone thinks about those things too or if he's just cheap. For the record, I'm also cheap and an aspiring old curmudgeon (currently lacking only age to earn the title), and that plays into it too.
On the original question, though, I have and use SystemWorks, but don't find it has any revolutionary effect on my computer and I don't find that the disk cleanup and defrag do any better than the utils packaged with Win2K. I bought it because I wanted Ghost, but it's such a pain, I don't actually use it and, once again, find that using the Win2K native backup is just as good. It periodically finds and deletes some unused registry entires, but it is miles from actually cleaning out the accumulated detritus in the registry. I would say for every 100 obsolete keys and values it finds one.
Sorry for such a negative response, but I haven't really seen much value from SystemWorks and wouldn't spend the money again (but then, as we've established, I'm cheap and a youngish curmudgeon).