I know a couple of people who set up Linux boxes for their elderly parents, and they've been working just fine for years now.
Also, most people don't care about using all the latest stuff, they just want something that can function as a word processor and internet terminal. Linux can do that exceedingly well.
And for the record, Ubuntu is a heavily modified Debian, which itself is probably the most "out there" distribution of the major players. It's the least compatible with ANY of the other distributions, even if you're using the testing branches. Ubuntu has already progressed to a point where it's largely incompatible with Debian now. If you use some of the more mainstream distributions like Fedora Core or Mandriva, you should be able to use nVidia's chipset drivers just like their video drivers.
OS X is kind of nice in that it's largely a black and white scenario with hardware. It either works or it doesn't for the most part. If you've ever dealt with "sort of working" hardware on Windows and the multitude of problems it often brings, it's a nice change.
Aside from gaming, there's no real need to have all the latest fancy hardware in your system, and this is exactly why I went back to consoles for gaming. Even if I went out and got an Xbox 360 Premium now, I'd get a complete gaming system for less than I could spend on just a video card for a PC. Games are all written to that specific hardware spec, so there's no risk of my going out and setting down $50 for some new game and it not working because my system is underpowered in some way. I don't need to worry about other programs conflicting in some way, bad video driver releases, or anything else. I buy a game, pop the disc in the unit, and away I go. I'll be a good half hour into a game by the time you get your PC copy installed. So I don't get all the latest graphics... How often do you stop to admire the scenery in a game?
Running Linux or OS X doesn't mean you have to give up gaming, it just requires a different strategy. One that can ultimately save a bundle of money. I have an Xbox, PS2, and GameCube... Even if I bought them all brand new at full retail, and the same with all the games I have for each (around 35 between them all), I'd probably still come out spending less than most people do on their SLI setups and I pretty much guarantee I'll get a lot more life out of my setup.
Anyway, that's my rant on the issue.