So does Leopard eat up Ubuntu? Or does Ubuntu trounce Leopard? It depends on your needs. If you're a student with no money, go for a decent cheap PC and put Ubuntu on it. If you value freedom above all else, then it's obvious-- Linux is the only way to go. If you're heading into a future in multimedia, you're gonna want a Mac. If your life revolves around your iPod and your iPhone, you need a Mac.Full Review
Ideally, though, you'll have both, since each offers features the other lacks. I use both every day. If you have the money, I would recommend buying a Mac with at least 2 GB of RAM and then immediately installing a virtualization solution that will let you run Ubuntu (and Windows, for when you just have to run Windows), as well as any other Linux you desire. That way, you can run two of the world's best operating systems at the same time, on the same machine, and bathe yourself in yummy UNIX-y goodness. And that, my friends, is just amazingly cool.