Didn't someone here on the forums make a bet about this feature? Looks like they better collect.
Using strikers Charged as an example, the gameplay was about 10-20 percent slower for me (but the game never choked), in comparison to playing single player. I'm assuming Brawl will take a similar hit, perhaps more depending on what options you have. For example, if you have item appearance set on high, that could impact the overall game. Fair enough, I'm not going to expect the impossible 1:1 connection. But I can hope....
Nevertheless, its a good announcement, let the updates keep comin'!