Pretty simple.
-Decent symbol distribution, obviously geared more towards the lesser-powered symbols
-More interesting theme support (kicks have always been made, but in my opinion, there has been no true kick support that has mattered)
-6 Handers, from this point on, being viable, if not THE most viable option.
-More Combos, in particular, ones that do more than just damage boost.
-MORE CHARACTER-ONLY CARDS AND ABILITIES!
That's about it for me.