I'm using Mandrake 8.1 on my primary "desktop" PC. I thought it was only for newbies until I tried it. It was then that I found out that Mandrake was better than Red Hat in every way. Up to that point I had been using Caldera for stability and NetWare compatibility.
I started with Slackware and kernel 1.0.8, and used it for quite a while. I used Caldera when the first public betas came out, and came to prefer it, especially after ISO images became available. I've kept up with Red Hat, with quite a few retail boxes to show for it. I haven't had the time to play with SuSE recently (I'm secretly pissed because the yellow-haired guy never comes to COMDEX anymore). I tried Debian, but never came to like it.
As for the "baby BSDs", I started with 386/BSD on an old AT&T server that I inhereted. I've done NetBSD on Alphas, OpenBSD on edge computers (before the RSA copyright expired), and FreeBSD on PCs for running sendmail. They're all OK, but Linux w/ GNU utilities has surpassed them all IMHO.