i have used Mandrake, Redhat, Debian (and progeny), Slackware, freebsd, openbsd and Solaris 8, no suse yet on desktop and laptop.
I am currently running redhat 8.0.
If you are targeting for the market, i would think redhat is good choice.
Since ibm products(websphere stuffs and domino stuffs) working seamless and oracle db(oracle 8i/9i) tend to support redhat first.
But cons of using redhat is u have to bear microsoft-like-linux. it means proprietary and
you should depend on redhat rpm and their sysv4 style configuration. Mandrake is a bit open source aware version of redhat. so mileages are similiar.
if you are rigourous about GNU original, you really want to get debian. GNU linux is actually debian linux, thus you can follow up and hack the source code and compile without mysterious errors. when you need to recompile the kernel or some
ide(gnome/kde/windowmaker), gnu linux doesn require headache since you just need to follow the README file for the package.
Slackware is really good choice,too for who wants to know hacking the linux codes.
If you want to get really stable version BSD and willing to some business with that, FreeBSD Unix isn't bad choice, too. Every linux materials from GNU is children of BSD. But i am not sure what the market of bsd look like right now.
Keep in mind, Mac OS X can run with FreeBSD. If you still like to use mac os x, u r using mac os x top of freebsd kernel.
Though sun server market is struggling because teh strength of linux, Solaris 8/9 has some advantage for solaris guys. you can download solaris 8/9 x86 version from Sun with small fees. Be aware that installation of x86 solaris is not that simple because they don't support lots of drivers for x86. i don't know what the sun is thinking about x86 solaris if they don't support rigourously.
OpenBSD is security enhanced version of bsd OS.
i 've heard the gov't likes to use OpenBSD.
The installation of OpenBSD is not that simple,either.
There is NetBSD, which i haven't had an experience about that. NetBSD is supporting more hardware drivers than those two bsds.
[ February 21, 2003: Message edited by: stephen Kang ]