The freeware CCleaner hasn't seen many major revisions since Piriform launched it in 2004, so when you do see a major update, you can be assured that it's going to come with impressive new tools. CCleaner 3 doesn't disappoint on that front, introducing two major new features that make it worth the upgrade.
One is a drive wiping tool that can wipe all the data from your hard drive, but can also scrub only the available free space. As with many of the tools in CCleaner, it's fairly nuanced and allows for a simple one-pass overwrite, a Department of Defense-level three-pass option, a National Security Administration-level seven-pass cleaning, and a 35-pass Gutmann-level deep scrub. The more passes you select, the slower the deletion process. Other changes in version 3 include improvements to the internal scanning tech that powers CCleaner, and the interface received some minor tweaks to make icons more visible. If you're familiar with previous versions of the program, though, you'll be hard-pressed to find any differences between older CCleaners and the new one. Additional minor changes include a new native installer for 64-bit computers, and environment variables have been added for %SystemDirectory%, %SystemDirectory32%, and %SystemDirectory64%.
Version 3 supports more Windows programs than before, including added support for Microsoft Silverlight Isolated Storage, AVG 2011, Audacity, LogMeIn Hamachi, BitTorrent, and Windows Game Explorer. Pre-existing support has been improved for Google Chrome, Internet Explorer 9 beta, and the torrent managing client Vuze.
For users who are new to the program, in addition to browser tracks cleaning it will clean tracks from other programs, empty your recycle bin, delete temporary files, and clean your Registry, quickly scanning for invalid entries before removing them. CCleaner will also back up your Registry before you hit delete, in case it accidentally removes a crucial component. There's also a basic, somewhat rudimentary uninstaller for removing any program on your machine. What Registry entries it doesn't catch, the main Registry checker will, but it's a two-step process that dedicated uninstallers handle nicely on their own.
In empirical testing, CCleaner 3 appeared to be marginally faster than previous versions. This is probably system dependent, so users with older computers could likely see significantly faster scan and cleaning times than in previous versions.
Problems with CCleaner are minor at best, and it remains a highly-recommended, must-have weapon against system slowdowns, tracking cookies, and the multitudinous debris that can clutter your computer.