On the whole, i enjoyed S2, but if I was to give it a numerical rating, I'd say 4/10, below average for Trek.
One of my bigger complaints would be with how watered down the Borg Queen was in terms of threat. We've previously seen Borg assimilation happen in mere seconds, and the assimilation of the Dr. took multiple episodes to resolve.
As for my biggest complaint, it'd be the setting. A jump to the past is a nice trip for a 2 or 3 parter in Trek, but a whole season just didn't jive that much for me.
On the other hand, S3, that was some of the best NuTrek I've seen so far.
Infrastructure I think. The last few waves of invites have brought instability to the system if i recall