I can't speak to multiplayer as I haven't experienced it but I think the Tali issue is being blown far out of proportion. Yes, it was an extremely bad call but I feel like it was motivated by pressure from EA and not a decision that the Bioware wanted to carry out. Truly though, why are people not more upset that they didn't do the fans a service by finally letting us actually see her face when she takes her mask off on the homeworld. *That* upsets me more and is more troubling than a last-minute poor decision.
I for one loved the entire game and felt it combined the best elements of 1 & 2. I even enjoyed the ending and had an extremely emotional reaction to it. Yes, it could and probably should have done more to tie-up loose ends and perhaps even represent the player's major choices throughout the game more but the realist in me understands that even within this fictional universe a single person can only have so much influence. The gears of intergalactic civilizations, once moving, are hard to affect.