It would be great if Han shot first again, it gave him a bit of a dangerous edge that completed his smuggler persona admirably. As for an amped-up lightsaber fight between Obi Wan and Darth Vader...I'm keeping my fingers crossed in hoping they pull it off in the right way.
I wouldn't mind a bit more elaborate swings and blocks, but I don't want to see Old Ben flipping over Vader's head and doing cartwheels. It just wouldn't seem right for an old man to move like he's still in his early '30s. It's fine for Yoda, (and it was fun to see in Ep II) but classic trilogy Obi Wan is just too classy to do something like that.