I'm currently using Pro on one computer and Enterprise on another. there's basically no difference in normal use. Main thing Enterprise and Ultimate have that Pro doesn't is BitLocker.
Funny thing I realized is I have used almost every single iteration of Windows OSes, starting with 95. 95, 98, NT, 2000, XP, Vista (for only one or two months, before switching back to XP), and now Win7. Technically DOS is an OS too.