Time and time again he's been the root cause of system issues. It's a proven fact that disabling Windows system files gains nothing in performance, so there's no reason to even consider it. Services in general should be left alone. Only in very unique situations, should third party services be manipulated.
In addition, Ccleaner has before, and can still potentially remove a registry item that you needed (Recently happened to me). It should only be used if you know what you are doing in the registry. I would highly recommend not installing this program as the performance gain from it is negligible at best.
Again, CCleaner has been proven many times over to be safe, as it's default scans aren't very deep at all. You also have a one click backup to any changes that are made. No one has ever made a claim that CCleaner is about performance, because it isn't, and is in no way related to performance. It offers several great tools all in one, and has been recommended up and down these boards, on actual Enthusiast boards, and even in trade mags. Anytime someone posts a thread about how CCleaner messed up their system, the solution is always something else. It's very safe by default.