For me personally I would like the admin section to be a little easier, there is nothing wrong with it as such but it can be a little clunky at the best of times.

Merging MU into Wordpress is a masterstroke in fairness, as it gives bloggers the ability to build a real community of people working together. Rather than your standard leave a comment and such like it will give the end user/visitor a real sense of contribution to a blog they love.

I cannot wait for 3.0, but then I am sad.