I'm a physical science major and im still in college. I started using Linux barely 6 months ago but I'v tryed most major distro's and some not so major. I'v seen a few other distro's based loosely on this same basis. Those being Backbox, Pentoo, Backtrack: (as far as i know) the most popular out there atm. I cant say that I'v tryed pentoo as its based on gentoo and if I wanted a gentoo pentesting distro I would just (I'm assuming) add the overlay and build the tools. That said I run Gentoo as my main OS on my desktop and rotate other distro's in and out of my extended partition. And I do more compiling on my desktop then I care to admit rite now trying to build a stage 3 that i'm happy with. I'v learned most of what I know about linux from this process (its very practical hands on learning for me). My laptop normally run's backtrack, I dont remember what it was, but I had some issue with backbox and havent toutched it since.. so. Anyway backtrack is extremely stable, and why not, its based on Ubuntu 10.04, and this is fine. The only thing i would say about backtrack is their comunity's lack of actual programming discussion. I'm fine with the fact that any 10 year old can download a copy, ask how to crack wep/wpa passwords etc and thats fine and good. Yet when I asked about programming i was told it was irrelevant and my post was blocked. This makes no sense to me as a distro geared towards pentesting you would think they would be all about this? I get the feeling that this isnt the case, and thats really kinda weird because if someone was into programming and knew Linux/Unix bash scripting / programming they would understand much more of how the programs worked, and therefore tweak them to their needs. As for Bash commands being different, i would say, and correct me if i'm wrong but it seems to vary slightly from distro to distro. From what you've said I doubt you would need this but it might help someone else out who stumbles across this thread i think.( web.physics.ucsb.edu/~pcs/apps/bash/intro-bash.html ) and.. correct me if im wrong but CentOS is more of a networking OS where backtrack is more Debian/Ubuntu like so i would assume small changes at least. As for paying for an education all over again? If you already have a computer science degree or something similar i think you know the answer to that. Just go with whatever you like the most, if you can program, get good and learn. Youll be a hundred times more valuable then someone who can click buttons on a pre compiled binary distro of Linux i would think. After i have bash scripting and programing down i figure ill get into either c or python, I'm not sure yet. From there I guess ill see where that takes me. Vi / Vim / Gvim Im sure would be good to know as well. Anyway good luck with that, just my thoughts.