I purchased a MacBook Pro a little over a year ago, and as tends to happen after a year of installing, uninstalling and reconfiguring applications, the machine hadn't been running quite as quickly as it did when it was brand new. I had already defragmented the hard disk a few times over the last year with some effect but it didn't seem to restore like-new performance to the machine on its own. Looking for more, I came across OnyX, a donation-ware multifunction utility for Mac OS which packages an impressive number of maintenance utilities into a single easy-to-use and attractive interface.

After launching OnyX, browsing through the Verify, Maintenance, Cleaning, and Utilities tabs will give you an idea of the many types of optimizations OnyX can perform. These items have descriptions and warnings where appropriate, to clue you in to what changes OnyX will actually make to your machine. Moving on, below is a screenshot of OnyX's nuclear option, the Automation tab:

Automate

Above are the settings I used on my machine. For safety be sure to go through all the descriptions in the other tabs before running all these to make sure you don't inadvertently make any changes you don't intend. In particular, the "LaunchServices" and "Display of folders content" options will reset some of your Finder customizations back to defaults and by removing logs and temporary items there is a slight possibility you will inadvertently remove something you need. As always, having a recent system backup is always a good idea when running any system utility. I was reasonably certain I wasn't going to lose anything important, so I left everything checked, except for the "Execute Maintenance Scripts" option. In my case (screenshot below), OnyX had already verified for me that my scheduled maintenance items had executed at their last scheduled times:

Maintstat

After clicking Execute and waiting for the processes to finish (about 15 minutes), my Spotlight icon indicated its index was rebuilding as promised, so I allowed that to finish (another 10 minutes) then performed the suggested system restart. The results were significant and immediately noticeable. All operations with Finder and the Dock are now as snappy as I can ever remember them being, Spotlight is blazing fast, and even 3rd party applications seem to start up and shut down more quickly than before. In addition to what I've discussed above, OnyX also offers on its Parameters tab some helpful interface customizations, similar but not quite as comprehensive as what you'd find in Secrets for Mac OS or TweakUI for Windows. The developer has forums available to handle support and questions. For me, OnyX did a great job and I look forward to continuing to use it. I found it well worth making a donation to support this independent developer's very useful application.