I am using CCleaner and System Mechanic. Does anyone have any opinions on which is better overall? CCleaner is fast and powerful, while System Mechanic has extra features. If cost is not a problem, which is better?

Better is a user defined choice. However I will tell you this; CCleaner is safer. I say this because I've seen System Mechanic's registry cleaner destroy the system registry on some systems by nearly removing all of it when only a few "invalid" references it found were removed.

There's also this thread CCleaner vs. Other Disk Cleaners.

I must agree, CCleaner is faster and in many ways more powerful than commercial tools. I have never had a problem with CCleaner other than not being able to delete some Norton Reg keys. Norton just seems to weave its way into your system like a parasite. Anyways, thanks for your input.