CCleaner, is it just FUD?

I have used CCleaner for years. I don't really think of it as a performance booster and I'm not sure that the developer thinks of it that way either.

The primary reason for using CCleaner is to remove the history of what you've been doing - starting with your browser cache, cookies, recently used file lists and many other logs and records. This is why it offers the option of overwriting the removed data up to 35 times! That's not about improving performance, it's about not leaving any traces. If privacy is a concern, it's a very valuable tool.

The registry cleaner is a secondary function but if you frequently install and remove software, it can surprise you with how many "dead" registry entries it will find and remove. I don't think this makes a big difference in performance, perhaps more of a benefit in reliability. It can fix problems that may arise when updating to new versions or with programs that connect to multiple file extensions, i.e. media players, etc.

In my opinion, it's worth using CCleaner occasionally (monthly?) if you aren't concerned with the privacy aspect - or very frequently if you are!

I wouldn't call it FUD, but the features that you describe are certainly becoming less and less necessary, in part due to what you already mentioned. However, CCleaner is a useful tool, if you know how to use it.

I regularly use it to fix installation issues where the installer will not work due to some leftover registry entries. Now I can go in manually to hunt them down, or do a sweep with CCleaner and let it do the grunt work--I have yet to see it fail to find what I'm looking for.

Of course, it also features a quick way of disabling startup items and from a (albeit on a low level) privacy aspect, the selective cookie cleaning is also nice. You can also download a community-built ini file that adds a lot more features to the cleaning tool, which is useful if you are a particularly obsessive cleaner.

Whether or not it aids performance, I don't know, as I haven't run any benchmarks. Perhaps placebo effect, but I do notice when I run it on client's systems who are not particularly IT savvy that the performance has increased substantially. On my own system, where I run it more regularly, I do not notice the slight performance boost it may warrant.

I mainly user CCleaner to free drive space when the drive is running low and just before I defrag the drive.

Doing a CCleaner just before a defrag mean the machine will not need to spend as much time moving "temporary" files around, plus the defrag program will have an easier time putting the non-temporary files in faster parts of the disk.

I know CCleaner helps with privacy (cookie deletion), but for performance, that is how I use CCleaner.