This time around, it’s nothing major, and no new features. WordPress 2.1.1 is a bug fix / security update release. With that in mind, you should take the time to upgrade – any security hole is potentially serious, and should be fixed immediately.
The WordPress team says this is a low-medium priority upgrade, but I say, why take a chance? It takes about 3 minutes to upgrade. Besides – what else would you be doing for those three minutes?