Gentoo, Debian, and Redhat.
I like Gentoo. gentoo rocks. Almost. For a personal computer it's great. Software technology changes so fricking fast that once a Distro releases a new version it's almost obsolete compared to a Distro that is going to be released a couple months from then. Gentoo is a good way to have all the nice new features and take active part in the developement and testing of new software. Since everyone sets their box up differently you are going to have people try most every fesable combination, and it uncovers bugs more quickly. The trouble is that you are going to get some instabilities. Bad compiles, ocasionally having to edit makefiles and the such. Software bugs that nobody has seen before and nobody will be able to help you make a workaround. Sometimes its tiring to have a OS thats only a couple levels above XP, in terms of stability. The Portage system is so good that it is practicly automation. Hit one line you get dependaces and updates. A simple update world command and come back a couple hours later and you have all the new stuff.
Now Redhat and Debian are good professional-level software. I would probably never use Gentoo for any server stuff at work. There is no point. Redhat has the advantage of uniformaty and corporate support, each time you install it it is very easy to duplicate software, it's always the same and even a lay-person after a couple installs will know what to do. If the OS fouls up during the install, help is a phone call away. It's a good OS for those inflicted with residual Microsoft-mentality. RPM's are good as long as they are from dependable sources.
Debain is just as good as Redhat for professional stuff, it just requires a different attitude from a comany using it. With debian and apt-get/dselect you can set up a server with any combination of software and cross-service plugins you could want in 15-30 minutes. Another couple hours later after modifing some configs you have a custom designed OS that will meet any specific need with complete stability and performance on pretty much any sort of hardware. Within a couple days to a week you can have a nice sized fully servicable lan set up, fully automated services with network monitoring and all that happy horse-hocky. Easy, quick, effective with any very knowlegble Admin and proper planning. All due to slighty obsolete, but well patched and tested software with excelent packaging system.
Gentoo for enthusiest who want all the flashiness that Linux can provide, it's has good system and capitolizes on all the strengths of Linux. Redhat is a good one that I have installed on my parents spare computer, for my younger siblings. I tell them that unlike XP that there brother can't screw up the computer and mess up their settings just as long as they remember to log out. I tried that on XP, but it only took a couple months before they all figured how to give themselves administrative rights. That computer is now slowly grinding itself into the dust. I am the only one that has r0o7 passord 😉, and I don't have to be there to keep the damn thing running and the couple times a month when I do visit, I can get new games installed and upgrade different bits without much hassle. And so far its stable as it ever is. Debian of course I have installed as the server for my personal lan, And it's my OS of choice for showing off for my boss, and its great on my old laptop.