Linux dominates the server market.
84% of the top 500 supercomputers run linux.
Of all the websites you've ever accessed, theres a big chance that the majority of cms's you've touched were on a linux server.
The majority of ILM's rendering power comes in the form of linux server farms.
The NYSE servers run on Redhat.
Oh and by next year, Russia will have brutally forced all their schools and educational intitutions to switch to some form of linux...
So whats linux good for otherwise?
Games, you can practically forget about that. In the desktop world, Windows runs the best games.
Office software, possibly, I've had no trouble with things like Open Office, although I know many people who have had terrible messups with it...
So ya, for everything else, its alright. But, it is true about hardware compatibility. If you just slap linux onto anything, you can expect it to throw you endless trouble, and your getting what you paid for.
Do not expect to just ram a linux distro into anything and have a windows experience. Unless you have more patience than the average joe and are willing to get down in the mud, your wasting your time.
If you want, it to work "flawlessly", then just like Mac works, I'd recommend getting something like those Dell laptops that come with Ubuntu linux preinstalled. Just like a mac, you'll have no problems with that. And I've heard the Asus EEE PC can come with Xandros linux preinstalled.....
So, ubuntu works with certain dells, mac works with macs, and windows works on more less everything else.
All depends on what your needs are and how far your willing to go.
Speaking as an Ubuntu, Fedora, Centos user.