I know this has been said a bunch of times, but I wanted to put in my two cents.
Speed up the recharge rates for all abilities, particularly for PvE. I know you want to create more balance in PvP, that's fine, but we shouldn't be able to get our grenades/supers only 2-3 times per strike.
Aside from this, I am really enjoying the gameplay in the Beta. The guns feel great, the new PvP mode is a lot of fun, and the game looks fantastic. Just speed up the power recharge rates and it will be excellent.