If you like Mandrake, why switch? Do you want to learn more about Linux?
Anyway, I use Gentoo and love it. I really doubt I'll ever switch distros again, and I've tried Mandrake, SuSE, Slackware, Debian, Arch, and Fedora.
Mandrake:
I liked it pretty well. Was a great way for me to get started with Linux. I mainly switched to SuSE because of all the problems 9.2 gave me, and I wanted to try something new.
SuSE:
It was decent. I found it a bit sluggish and buggy, but it wasn't too bad. I think why I switched to Slackware was I wanted to learn more about Linux, and I got annoyed with SuSE for tweaking stuff a lot and that sort of thing.
Slackware:
I used it for a long time. It was nice. Taught me a lot. It ran well, quite fast. I switched to Arch because Slackware didn't have too many packages, and because swaret hosed my glibc, and something else, twice in one week. (Really my fault... but I got quite frustrated) Oh, and because Chinese support wasn't working too great with it.
Debian:
I tried it for about a day. I couldn't really get it installed, not the GUI anyway. It was big and confusing. Even the main installer confused me, and I knew quite a bit about Linux at that point. I went back to Slackware and continued using Slack for a few months.
Arch:
It was really nice. Nice forums, nice website, nice amount of packages. It was hard to set up, took me awhile, now I could do it faster.. it taught me even more than Slackware. Pacman is a great package manager. It worked good apart from Chinese language support. Maybe I just was too dumb to get it working, I think I would be able to now... but not sure.
Fedora Core 2:
Clean, professional. Nice if you intend to use the default desktop (Gnome) with the default theme and icons (bluecurve) and never really change themes, or install much of anything, but that is only my opinion. Fedora's KDE is kind of buggy in my opinion, I couldn't get the menu editor to work, among other things. Gnome has some problems too. Chinese support was much improved but I had lot of problems with Chinese music files. And, everything is only i386 optimised.
Gentoo:
As far as I can see, I'm sticking with Gentoo. Chinese works the best of all distros. It's fast. It's stable. Portage is great. It is really non-bloated, it gives you only what you want, so you aren't going around with 5 web browsers, email clients, text editors, music players unless you want them. You can install exactly what you want, nothing more, nothing less. You can compile applications/kernel with the support for just what you need, not with stuff you don't need, or lacking what you do. It's up to date. Portage has almost everything.
Only downside, for me, is compile time.
It all depends on what you want.
If you haven't already, check
DistroWatch to see pros and cons of the common distros.
Hope this helps.
Mary