It's pretty much useless in every respect. You don't need "cleaner" or "maintenance" apps to keep your Mac running well, and some of these apps can do more harm than good. Some remove files/folders or unused languages or architectures, which does nothing more than free up some drive space, with the risk of deleting something important in the process.
These apps will not make your Mac run faster or more efficiently, since having stuff stored on a drive does not impact performance, unless you're running out of drive space. Some of these apps delete caches, which can hurt performance, rather than help it, since more system resources are used and performance suffers while each cache is being rebuilt.
Many of these tasks should only be done selectively to troubleshoot specific problems, not en masse as routine maintenance.
Mac OS X does a good job of taking care of itself, without the need for 3rd party software. Among other things, it has its own maintenance scripts that run silently in the background on a daily, weekly and monthly basis, without user intervention.
You don't need any 3rd party software to keep your Mac secure. Macs are not immune to malware, but no true viruses exist in the wild that can run on Mac OS X, and there never have been any since it was released over 10 years ago. The only malware in the wild that can affect Mac OS X is a handful of trojans, which can be easily avoided by practicing safe computing (see below). Also, Mac OS X Snow Leopard and Lion have
anti-malware protection built in, further reducing the need for 3rd party antivirus apps.
- Make sure your built-in Mac firewall is enabled in System Preferences > Security > Firewall
- Uncheck "Open "safe" files after downloading" in Safari > Preferences > General
- Disable Java in your browser. (For Safari users, uncheck "Enable Java" in Safari > Preferences > Security.) This will protect you from malware that exploits Java in your browser, including the recent Flashback trojan. Leave this unchecked until you visit a trusted site that requires Java, then re-enable only for the duration of your visit to that site. (This is not to be confused with JavaScript, which you should leave enabled.)
- Change your DNS servers to OpenDNS servers by reading this.
- Be careful to only install software from trusted, reputable sites. Never install pirated software. If you're not sure about an app, ask in this forum before installing.
- Never let someone else have access to install anything on your Mac.
- Don't open files that you receive from unknown or untrusted sources.
- For added security, make sure all network, email, financial and other important passwords are long and complex, including upper and lower case letters, numbers and special characters.
- Always keep your Mac and application software updated. Use Software Update for your Mac software. For other software, it's safer to get updates from the developer's site or from the menu item "Check for updates", rather than installing from any notification window that pops up while you're surfing the web.
That's all you need to do to keep your Mac completely free of any Mac OS X malware that has ever been released into the wild.