"Free, fast, secure, smooth, pretty."5.0 starson by Temugin1982
Pros: More secure than Windows, cheaper than a Mac (well, 100% cheaper), and as fast as both. Doesn't slow down over time like Windows, doesn't require anti-virus, IT'S FREE, be happy that you are not buying into Apple or Microsoft's world domination.
Cons: Adobe don't support Linux, so no Photoshop. But if you can live without Photoshop (GIMP and RawTherapee do for me), then Linux Ubuntu really is all you need.
Summary: If you can live without Photoshop then save yourself some serious money and use Ubuntu.