When I bought mine, I was because I wanted (note wanted, not needed) a notebook/laptop.
I don't game, and anything I do is more than capably handled by the Macbook.
Basically, I wanted a laptop that "does" OS/X, without all the fiddling and headaches of a Hackintosh. I wanted the "real thing" this time around.
I also couldn't justify the large price differential between a MB and a MBP. Heck, if a MB was good enough for my geek IT/Unix friend, it's good enough for me!
Love my little white lappie, LOVE that it's not aluminium, LOVE the keyboard, LOVE that the RAM and HDD were so easily upgraded.
Call me shallow, but I also LOVE the attention she gets when I take her out and about. I love seeing Windows people say "hey it's got WINDOWS". Well, duh.
Do I want a MBP? Of course I do. I don't need one though, just as I don't need an iMac. This machine does all I could ever ask of it, PLUS I can take it with me (although I don't as much any more, now that I've got a Touch).
The MB is a solid little computer. 'Nuff said.