ASC is a program that is definitely well known, and I've not heard anything bad about it from anyone of my IT buddies. While I'm sceptical of a lot of the things it claims to do, I do know that certain things are effective. I'd say a few things (like the spyware removal security defense scans) are probably not the most effective, compared to various specific software you can get, but I'd say it's probably still a decent software overall.
I've been using the Pro version for a few months now, and I can't really complain. Have I really seen that much improvement on my computer? Well, I'd have to say that is entirely subjective. In certain cases, my computer doesn't seem to lock up as easy; although, it hasn't really made anything faster or more efficient (not significantly). I'd say it's a good tool for basic maintenance, and for preventative measures.
The uninstaller from IObit is definitely a damned good program. I have run a number of free uninstallation programs, and found nothing that really did a thorough job. I used to have to clean everything manually, and I hated it. It's made cleaning up hard drives so much easier. For example, I always upgrade most of my programs manually. Whenever I'd want to do an upgrade/reinstallation, I'd have to spend about 20 minutes just tracking down everything to remove the last bits of crap, then install the new one... and then do it all again with each update I made. Eventually, I stopped bothering, and my installs were never the same. This has pretty much taken care of the problem. I wouldn't say it's always going to clean every crumb of an installation, but it's definitely going to catch more than most software could.
IObit is a quality company, and they also offer some great tools for more advanced users too. Definitely a good company.