DW and Onyx
I use Disk Warrior (run while booted up from an external firewire HD) and Onyx.
Onyx has several functions that do not need to be run all the time, or only when there is a related issue. The maintenance scripts get run by the OS, but if you want to run them, Onyx makes it easier than pasting them in to a terminal window. Onyx can also make it easier to delete caches etc,. a common "try this and see if it works" type of thing, which does work if the issue you are having is due to a corrupted cache. In any case having Onyx and using it to delete the browser cache and history, the logs and the misc. items can delete up to 700 files, so I run that function before backing up my home folder. I have never noticed any speed increase after using Onyx.
I run Disk Warrior occasionally to optimize the directory and as a preventive type of maintenance, to catch disk errors before they become critical. This does give a slight feeling of a speed increase, but it doesn't last long and may be a false feeling. However, Disk Warrior is the best in its field for recovery from a bad crash, and it is nice to have on hand just in case.
Still, no maintenance whatever can take the place of having a proper backup, hard drives die, sooner or later, it is just a matter of time. Sometimes you get lucky and the drive lasts longer than the other hardware, sometimes not.
