I'm quite happy with the free version.
Over the years I've tried one "free" registry cleaner after another. Many of the so called "free" software will report that it found 23 million errors but can only fix 7 for now. If you want the other 22,999,993 fixed you'll have to buy their software. Sure thing.
Another free program that may be of interest is
Revo Uninstaller Free. It removes programs in 3 phases. First it runs the unwanted programs uninstaller. Then it scans the registry for left over bits. Finally, it scans the hard drive for leftover files and folders.
You would be VERY surprised at the huge amount of registry items that it'll some times find.
BTW - the registry cleaning didn't make any difference for the FSX Global/FSX problem. Didn't think that it would, but I use CCleaner whenever I run into problems because it'll sometimes make repairs, not just remove old unused bits.