I'm going to have to chime in for SuSE 9.1 Pro.
I just got it in at work and it's quite streamlined and user-friendly.
I've already implemented it in my company's warehouse for running
5250 emulation as well as vt-220 emulation.
It comes with the 2.6 kernel, as well as the latest KDE (3.2) and GNOME (2.6?).
Installation was a snap except for choosing packages. That's where YAST (Yet
Another Setup Tool) is lacking still.
The other aspect that I am disappointed with is the amount of memory KDE now uses.
256MB is already overflowing by the time it gets entirely booted up. Just
make sure you have plenty of memory.
People are chiming in for Red Hat, but I lost my taste for them when they
turned the corner and became strictly enterprise.
Sure they contribute to Fedora, but only as a testing ground. Once new software is proven
running in Fedora, they implement it into their Enterprise server. Pretty smart, but still disappointing.
SuSE 9.1 is my current flavor of choice (I also enjoy Knoppix 3.4, Knoppix STD 0.1, and
Gentoo 2004.1) but I can't vouch for Mandrake 10, as I've never tried it out.
-jeff