Also, when you buy it, you get a set of books called manuals that explain how to do things, which often have more information than the online help. And, if you don't have two monitors, it's the only way to edit something full screen and read the reference material at the same time (barring printing all that crap out).
Now that I have a job and can actually afford to buy software, I've decided to stop cheapscating.
--WetWired