I have Leopard 10.5.3 on my PC. I use it occasionally, now that the novelty has worn off.
As far as installation, I think that the ease of installation is highly dependent upon one's particular hardware configuration. My hardware seems pretty well adapted for OSX, but others seem to have a devil of a time getting it to run.
Everything went fine for me, even though I'm on an AMD CPU. Luckily for all my other hardware, there were drivers for (audio, ethernet, USB.). My video card isn't supported though in leopard (it is in Snow Leopard though).
I wanted to install Linux on my other desktop computer before, it's an Intel Dual Core. I did hear from my friends that it's pretty complicated though, some friends even told me that I should build up my own GUI or something like that, and when something goes wrong, I have to take time to fix it myself (which is really hard of course).