This will be interesting to see. Both of their power sets are pretty tricky to show live. Quicksilver's superspeed has been done before, but not very well IMO. Making him race while everyone else is moving at normal speed could look silly. And Wanda's hex powers of probability are hard enough to explain to people, let alone show on the big screen. I'd be concerned that the average Joe who doesnt know her wont really get her powers.
She'll also offer fanboy eye candy.
Got preview tix to IM3 for Wed evening. My son is more excited than I.