You probably don't need BitLocker and you probably won't need to set up each of your comptuer's user accounts with a different language. Then again, if you're getting pro, ultimate is only $20 extra. Personally I wouldn't buy ultimate, and I voted so in the poll. I'm thinking most people voted for it because they thought it had the most features or they wanted it for bragging rights or something but Windows 7 has a very simple feature ladder - pro has all the features of home, ultimate has all the features of pro. You're not going to miss out on home features by upgrading to pro (unlike vista, or so I've read, I never used vista).
I can basically guarantee you will not use any of the ultimate features and that it's a waste of your $20 unless you're putting it on a company laptop where having an encrypted hard drive for business makes sense and you need to be able to switch between languages on the fly is if you've got a client in another country and want to show them a presentation or lend them your laptop for something.
XP mode is useful and if you think you might use it then go with pro. Otherwise stick with home. The difference of $80 is pretty significant.
Also, if you've got a family member in college right now you can get the upgrade for $30.
Poll