Some people in this thread seem to misunderstand the um, utility, of these utilities. Sure, you could probably get along without them, and you can certainly replicate most everything they do with Terminal, but they are easier to use.
I don't have need for tweaking maintenance scripts, although these will do that. What I've found them handy for is nuking caches. I recently had a borked font cache, for example. And also a QT snafu. I could search out where these caches are on the internet and then run a rm in Terminal, but these make it much faster.
MacPilot is also significantly different than the other two. It has customization features not only for the system software, but also third party applications. I've used it to tweak settings you can only access via Terminal or manually editing plists, and to edit file attributes and things like ACLs. It has a database of error codes, and access to things like open ports. Again, I could get that stuff in other ways but it's nice to have it in one spot. I'd recommend you download and give it a try; it can be a real time saver.
And BTW, I have to disagree with someone who mentioned that utilities like DiskWarrior were obsolete. Maybe for him, but it recently saved my data when a drive failed. It was a laptop, so TM didn't help since I wasn't connected. Disk Utility and fsk didn't repair it, but DW was able to rebuild the directory well enough for me to save files. Certainly a backup is better, but we don't always have access to one.
