Stephen Vaughn-Nichols has written his opinion of 3.1 in a ComputerWorld article.

I appreciate his conclusions:

I’ve been using for years now. With these performance and appearance improvements, I can see more users moving to this free office suite. In particular, I think anyone who does spreadsheets every day owes it to themselves to compare Calc and Excel. You’ll be impressed.

Calc aside, 3.1 isn’t a major step forward. But if you’re getting tired of paying for a new version of Microsoft Office every few years, you should try this latest edition of Except for advanced presentations, there’s nothing you can’t do in the free that you can in the ever-more-pricey Microsoft Office.

You and your school are using/considering, aren’t you?