The new review feature is interesting, and I have experimented with it. I have a number of concerns- I wonder whether my concerns are shared, and whether there is anything that can be done to address them.
My primary concern is that, if one wants to review, one is presented with a random question/answer which is probably out of one's area of expertise. The right thing to do is to "skip". But the system is gamefied in such a way as to incentivise taking action anyway. If a question or answer "looks" bad but is actually good, I'm pretty sure that this system significantly increases the risk of incorrect closure (perhaps even deletion); especially as other people's votes are not visible. This appear to me to be a serious problem, which the previous incarnation of MO didn't have, certainly not as badly.
Additionally, we are asked to review first posts by new users, and late answers. But users who are new to MO are not necessarily new to mathematics. It seems strange that we should have to review a first post by a great and eminent mathematician just because they are new to MO. Also, in mathematics, it sometimes takes time to work things out. I'm not sure that late answers are necessarily suspect (although this feature does provide certain utility to clean up old questions and answers).
It makes more sense to me, for example, that we should review answers with zero or negative votes for a a long time (over a few weeks) to see whether they are in fact answers, irrespective of the experience of the respondent.
What do others thing of these new features?