It's the day before release and the reviews are starting to roll in:
Gamespot: 6/10 IGN: 7.7/10 GameInformer: 8/10 Polygon: 7.5/10 PC Gamer: 80/100
The common criticisms seem to be that there are technical issues, they don't like the supporting characters, and they feel that there aren't enough "big decisions".
I feel that reviewers have gotten into the habit of overplaying technical issues. I find that often they are playing on a non-final build, and naturally those builds have less polish. Essentially, if they don't keep the game from being fun, they should affect the score too much. It seems that the penalties given here were pretty harsh.
We'll see about the supporting characters. I do think it will be hard to beat the original series in this area.
The whole "big decision" criticism has frustrated me for a long time. I have noticed that people want their actions in these games to have enormous consequences such that the universe would not be recognizable without them. The fact is that there are limitations to this. A developer cannot make the consequences of decisions so large that they cannot be reconciled in future entries.
For now, I'm not putting much stock in the reviews. I think that reviews are often more affected by the expectation of what the game would be rather than the quality of the game itself when it comes to series like Mass Effect.