Onyx (freeware) and YASU (donationware starting at US$3.50) both clean out errant cache files and do simple maintenance that would otherwise take a good deal of familiarity with shell scripts in the Terminal application. Both apps do a good job, but can be complicated and are focused only on cleaning cache and log files.
AppCleaner (freeware) and AppZapper ($12.95 for one license, $18.00 for two and $79.00 for ten licenses) are both similar programs that make sure that all the little ancillary files get tossed away when you're deleting an app. This is a problem with most Mac applications, since the great majority of them put all sorts of little .plists and assorted junk in hard to find places. Most people I know just trash the application and say it's good. It's really not, since over time your hard disk gets littered with all sorts of junk files that never get used. AppZapper is current, but no one has updated AppCleaner since 2008, so I don't know if I'd trust it.
This is far from a complete list of cleanup utilities since there are many other similar programs out there, but a major point is that only CleanMyMac is one stop shopping for getting it all done. It's constantly updated, so there's no worry about it missing something or getting something wrong. One slam I've heard about CleanMyMac is that it's dangerous and has caused people lots of trouble, especially when deleting languages. This is a specious argument since in every case I've read, these problems were due to the user not paying attention, deleting every language on their Mac, and blaming the program when nothing would run properly. Yes, it is possible to do this, but I would expect anyone using such a powerful suite of utilities to pay a bit of attention, especially since there are warnings galore. In the latest version of CleanMyMac (1.9.3), Macpaw made it impossible to delete the English language. This doesn't sound like much, but this built-in safety net is quite a help by forbidding you to commit digital homicide.
Most other programs just go along and do their thing with no user feedback, but CleanMyMac gives you a huge amount of information when you want it. After running a scan, click on any tab and you'll be able to see every file that it wants to delete. If a folder is displayed, you can expand it to see all the files in it and remove check marks so certain files won't be deleted. None of this gets in the way if you don't click on a tab. After using the program for quite some time, I no longer click the tabs since I trust CleanMyMac to do the right thing. To date, it always has, and hasn't caused me a lick of trouble. What CleanMyMac has done is to teach me quite a bit of what's going on under the hood since I've become familiar with names of files that always seem to come back and have no discernible purpose.
CleanMyMac also has a few other useful features. Under the tab Manage Extensions you can view and delete (if desired) widgets, preferences and plug-ins. I would suggest using caution when playing with this tab, but it is nice to know exactly what files in these categories are installed on your computer. If you find something you haven't used in years and don't need, Manage Extensions gives you a clean way to get rid of it.
So how much space can you save with CleanMyMac, and does it really speed things up? The first time I ran it on my Macbook Pro after periodically using some of the other programs mentioned, I recovered over 16 GB of storage. Even with hard drives getting bigger and cheaper, that's still a massive number. A lot of the savings were due to eliminating languages that I would never use and deleting universal binary code. Universal binary programs contain both PowerPC and Intel code. Since you only have one type of processor in your Mac, deleting the code for the one you don't have (most likely PowerPC) can halve the space a program takes up on your hard drive, and any extraneous code will never be run. Deleting binary code made my MBP run noticeably quicker, which makes sense since the Mac is dealing with less code.
After the first time you've run CleanMyMac, how much more space can you save? I just ran CleanMyMac a few minutes ago (I use it weekly) and it wants to free up 1.06 GB -- that's a pretty good amount of space. If that's what it can do in one week, just imagine how much space CleanMyMac could save if I ran it after not running it for a few months.
CleanMyMac contains a number of safety valves. If it has determined that it wants to delete a file on its internal gray list (a constantly updated list of things that might cause trouble), a tab might show that it wants to delete 24 MB out of 37 MB total. It's then up to the user to click on the tab, take a look at the contents, and decide if they want to check some questionable items for deletion. If you do this, a warning screen pops up explaining the implications. If you know what you're doing and want to trash them, fine. But you've been warned that there might be problems. There are many similar features in CleanMyMac that can keep you out of trouble, which is a very good thing indeed.
There are a few annoyances (at least to me) that others might consider features. To do a thorough cleaning, you'll need to authenticate by putting in your system password. If you set preferences to fully delete any program you've tossed in the trash, and then actually delete a program, a big honking window appears displaying all the little files that will be deleted and asking you one more time if that's what you really want to do. In the majority of cases the answer is yes, and I would be happier if it was possible to turn off this nag screen in the preferences. You also have the option of clicking the Uninstall Applications tab, which lets you drag a program into a waiting window to display the extra files, but I don't see the point of that since dragging an app to the trash without running the program is enough for me.
Another annoyance is the registration/de-registration process. When you install a registration code, CleanMyMac does an Internet check to see if the registration is valid. No problem there, but there is no way to de-register the program if you want to stop using it on one computer and start using it on another. To do this, you need to email Macpaw, who to their benefit are quite responsive. I would rather they used something like the method Equinux employs. That software company also uses online activation, but also gives you the option to de-activate an installation from within their programs. This is a far more elegant method and I hope that Macpaw is paying attention.
Pricing is a bit odd and complex. You can purchase a six month license for $14.95, a lifetime license for $29.95, a two computer license for $49.95 and family pack of five licenses for $74.95. I know that flexibility is nice, but more than one user has complained that after using CleanMyMac for awhile, Macpaw is always asking them for more money. Silly rabbit -- they bought a six month license.
In the final analysis, CleanMyMac is the best piece of utility software I've ever bought. It's easy to use on a basic level, and on a more complex level it allows more knowledgeable users to fine tune their hard drives to be as skinny as a fashion model. CleanMyMac takes great pains not to let you get in trouble and works exactly what as advertised. I couldn't ask for more.