Linux
I recently installed Ubuntu 8.04 on an old P4 laptop, nuking XPsp2 in the process. I know (basically) dick about Linux and got it working straight after the install. It picked up all the hardware, wireless USB, extra-fangly-dangly "media" keys; everything. I must say, I was stunned. I was expecting unarmed combat with bash scripts. Nope. I just worked.
I fed it a wifi USB dongle, and unlike Windows which had a hairy blue fit with the same dongle, Ubuntu gave it a great big hug and asked which network I wanted to connect to. No drivers, not ini files, no crap. Lovely.
I then decided that I wanted gizmos. Real productivity tools like wobbly windows, y'know, the essentials. To do this I used the Ubuntu equivalent of on-line Microsoft Supprt (i.e. the forums). Took me about 30 mins for this "essential" work. Not too bad really.
I now have a pretty speedy laptop which does everything I want, and I look forward to learning more about Linux and how the various windowing apps etc. all hang together.
Comparing Linux to Windows, I would say there are three main differences:
1) Windows tries to blur the line between the OS and apps. People think their window or media player is the app. Linux does not do this. The OS is the OS and the windowing system is just an application on top. That takes a bit of a mental shift.
2) Linux documentation assumes a fairly high level of competence and is not beginner friendly. Not that beginners really want to hack Linux, but there are times when I wish the install docs were a bit more clear on exactly what I have to do to install an app, not just say "Download tar and install"
3) Variations. The are more flavours of Linux than you can shake a stick at and this can be daunting. Which one do I choose? Will this guide for SUSE 10.3 help me with Red Hat 9? There is a similar issue in the Windows world, it just isn't as pronounced.
Finally, the vendors. Yes, Dell do sell Linux kit, but it is not easy to find (not as easy as the Windows kit anyway) and it is almost as if they are embarrassed by it. Which is a shame, because from my current experience with this old laptop, Ubuntu knocks socks off XP (and probably Vista too).