Windows
After I put debian on my desktop computer and bought an ibook for a laptop. I stopped using windows completely. The NT family of OS's were solid, and I never really had any problems with XP. On the other hand, I didn't have any problems because I was very careful with what I did on that computer. I haven't kept up with Vista at all.
OS X
I think Apple's done a great job of make a day-to-day OS for dummies. That way, when I want to feel like a dummy and not obsessively configure (see linux) every freaking detail, I can just make some common sense assumptions and start working.
Linux
Sometime before high school, my dad brought home 2 O'Reilly Linux books. He never looked at them again after he wrapped them, but told me that *nix was important. This confused me since he was a Windows admin guy. The book was on RedHat 5.1 and I installed it on my newly upgraded Pentium MMX 233/266Mhz machine. I got really excited about the philosophy and freeness the books touted. Watching Gnome start up, and something non-Windows on my computer was also a treat. Fortunately for me, those early windowing apps were absolute garbage. This forced me to the command line and made me learn how to get around without a GUI. I remembered my DOS days very fondly, so the transition wasn't a big deal. I remember having a heck of a time getting a floppy to mount in Linux. I had to ask Sean's dad (a Berkeley professor!) because it was so frustrating. Man pages aren't designed for impaitient noobs. RedHat was a gateway drug for me. I moved on to try several different distributions. At the time, I tried them haphazardly and didn't really know what I was looking for. I judged each distribution by how hard it was to install and how easy it was to get software loaded on it. The RH book totally lied about RPMs. I tried Slackware and enjoyed the packaging system much more than RPMs. When I volunteered for the ACCRC refurbishing computers for nonprofits, I installed Suse 7 on those machines. After I tried Debian Potato, I was pretty hooked. Woody was even more amazing (fresher packages). Even today, after Ubuntu has redefined ease of use, I continue to use Debian because I see no reason to switch.
640K ought to be enough for anybody - incorrected attributed to Bill Gates
DOS was an easy to love operating system. Any negative brought up against DOS
can be "scoped out". I didn't miss multitasking; It had graphics and
sound;
Platform of Choice
I kept some rants and notes to myself a while back about what I thought about some of the operating systems I've used and currently use. These notes are more about day-to-day usage from the perspective of a software developer / power user rather than an objective review of each platform. I also update these pages with links to my favorite apps and tricks I've come across.