I have tried almost all of them:
SuSE, Mandriva, RedHat and Fedora, Slackware, PCLinuxOS, Linspire, Vector Linux and some few other and it never fealt like it was totally up to par with Gentoo.
I have been using Gentoo since 2002 (after I tried Mandrake, RH, SuSE and Slackware) and it stuck!
Since then I tested said distros on a regular basis but never again did it feel "right". The power was lacking, and sometimes the GUI interfaces messed up the distro beyond repair.
The latest versions I'm testing is SuSE 10.1 and the latest Mandriva. My one friend swears only to Mandriva, funny though, he constantly reinstalls everything, about every 2 months or so.
The beauty of Gentoo is that this machine has not known a reinstall since late 2004 and it is more up to date than the latest binary/rpm distro availble. This is through hardware upgrades and hard drive upgrades (even the root hard drive) and I only reinstalled to see what the fuss was with the latest LiveCD installer.
The history of this machine:
It began as a Athlon XP +1700 socket A on an Asus motheboard with 40Gb Maxtor harddrive.
Then it became a Athlon +2500 Barton Socket A on a Gigabyte and Chaintech motherboard with over 600Gb of harddrive space.
It then went from a +3200 socket 754 on a MSI motherboard to a +3200 socket 939 MSI Diamond and it now finally sits as a +3800 x2 on the same motherboard.
AMD +3800 x2 939 CPU
MSI K8N Diamond motherboard
2Gb KingMax performance RAM
Nvidia 7800 GTX 256Mb GFX card
2x SATA Harddrives (200Gb Western Digital + 200Gb Seagate)
1x SATA Samsung DVD+R/Rw
450W Antech Smart Power
Not sluggish at all, and everything works 100%!
To sum it all up, I have no desire to work on another distro, but I love trying them out. I love to see the new inovations and to tease the shortcommings of some, but I will always (so it seems) remain a Gentoo addict!