The technology behind KDE4.x is certainly several steps ahead of Gnome, but in terms of stability, I've yet to use KDE4 for any period of time without dealing with multiple application crashes. Whether this is a KDE problem or the applications themselves, I'm not sure, but it keeps me tied to Gnome for the time being for my day to day needs.
Glad to see someone mention these two gems. System Shock 1/2 and the Thief Series were among the best games released during their time. The day Looking Glass Studios closed their doors was the day that a significant portion of my faith in the PC gaming industry died. It seemed sick and cruel that such an innovative company could wither and die due to lack of profit while Blizzard ranked in cash hand over foot with a mediocre sequel to a mind-numbingly boring game (Diablo II).
I'm not sure this is entirely accurate. That main convergence between RHEL and other distros is that RHEL is NOT designed as an all in one system - desktop, media center, internet, etc. It's designed around, as you said, enterprise use. You have server, adminsistration, and development workstation setups, but it is in no way designed to be a standard desktop replacement the way Ubuntu and similar distros are.