The cinematic trailer
for DCUO is quite amazing. I also think that the backstory explaining why there are suddenly thousands and thousands of super beings running around the world is also a genius. The followup
brings a bit more depth to the story. At first I was wondering which DC Character is hanging out with Lex... but then I realized it's not a canon character -it's a "New Hero."
As for character types, each player receives an Exobyte, which contains a specific power set... so everything has to fit into a limited power descriptor. Of course, the Exobyte thing does get a bit hand-wavy about all the Green Lanterns and Gadgeteers running around.