The install, while not yet one-click, is fairly simple to do and works with a standard Leopard DVD. I've certainly gone through worse Linux installs. And when you're done, it might as well be a Mac - Airport, webcam, Quartz Extreme/Core Image, scrolling touchpad, even the special function keys work. Hell, the thing wakes faster than my MBP, too, and does the same creepy pulsating-sleep-light as well.
The only downside with the Mini 9 specifically is the bizarre keyboard - there's a really thick border around the edges , which cramps the keyboard and forces it to use odd-sized keys, pack them too close together, and arrange them with apparently little thought - keys like the apostrophe/quotation mark are down by the left arrow key. You can get used to it, but if you want to run a Terminal session you're going to swear a lot.
Some of the other netbooks do have better keyboards, but none of them have the near-100% compatibility with OS X the Dell has - there's always at least one piece of hardware that's non-functional.
Overall, I'm really impressed. I'd heard OS X was easy to install and runs well, but it was still fairly mind-blowing to actually see it run as well as it does. If the netbook concept intrigues, a Dell Mini 9 running OS X seems to be as good a choice as any. (Excepting that damn keyboard.)