Alot of those programs sound really useful, any comment on ones that work good or dont work good ?
Well, personally, I'm not still too impressed with WhatSize. I've tried it a couple of times in the past when trying to help other people on these forums, and it was absolutely atrocious. Serious bugs and design flaws resulting in completely incorrect output.
I just tried it again, curious to see if they'd fixed their problems. Was looking good, nice impressive new interface, when in less than 2 minutes of use it crashed on me. Oops!
The output seems more correct this time around, and I see they did implement one major fix I'd suggested in this forum
back in April. But for anyone who's not afraid of Terminal, everything it does is available for free with the built-in
du command. $13 for a pretty interface? I'll pass! Others may find it useful.
As for the other apps, most seem like things I'd rather try to figure out on my own for fun. KeyCue looks handy, but it's clearly just looking somewhere in the application bundle for that info. Would be fun to research what it's looking for - probably not hard. MacPilot looks like somebody went to
macosxhints.com and put a bunch of the hints into one app. And they charge 20 bucks for it? Sheesh.
In fact,
daenney seems to have it right on most of them, from what I can tell. Especially iVolume... huh?

Isn't this built into iTunes?
DriveGenius does seem to be the most promising, but I have no direct experience. It's made by Prosoft Engineering, who also makes
Data Rescue II which I can personally vouch for as an excellent product. Saved my butt when a drive started to go really bad.
Out of curiosity, I just tried the demo of DriveGenius. The gratuitous eye candy is a little over the top for a drive utility...

I also find it hilarious that even a product like this with real, non-trivial features has to add stuff that already exists in standard system utilities (Info and Initialize). I'm not sure what they can possibly add to initialize/format to make it any better than what Disk Utility does?? But otherwise it looks pretty solid, and easily the best value of this package.