Like them or not, they're not worth complaining about.
Personally I enjoy seeing how the assets are updated, S2HD or Not. I think people are just frustrated by a lack of transparency. Obviously the S2HD Team has no obligation to provide updates to anyone, or even exist for that matter, so nothing to complain about there... However, I think fatigue is reasonable considering the project has been ongoing for 7 years, and such a small amount of progress has been shown.
If I were the Sonic 2 HD team, I would make a couple new wallpapers using the new assets, in a new Zone. So, we have wallpapers from EHZ, how about a mock-up of HTZ with the new assets, or chemical plant for that matter. The general silence and timeframe has people rightfully assuming the project is either dead, or will inevitable die, so it's hard to maintain any excitement.
Correct me if I'm wrong, but wasn't it stated not that far back that something bigger was on its way in terms of a reveal?