1up has just posted the most detailed preview of Lego Universe I've yet seen. The idea of collecting different blocks in the world so that you can build more stuff has my inner explorer titillated. I also like the idea of bopping around worlds with wildly different themes (e..g., Pirates, Space).
I also wonder of a game with such a simple character development system will be able to hold my interest. You basically collect hearts to increase your health, and collect items to earn new special abilities. It sounds very Zelda. Of course the Zelda games were slightly awesome, so maybe I'm worried about nothing.