IMO,Year zero is a step in the right direction. It's no masterpiece, but is certainly a breath of fresh air after the extremely dissapoointing with teeth.
Expectations play a big role in my ability to appreciate something though. I was expecting the worst, and this album is quite good. The lyrics are still more linear and literal than we've seen from Trent in the past, but are decent. There are some classic NIN sound paradigms in this album, whose reappearance I appreciate without being a straight regurgitation of older albums.
I've been listening to it fairly steadily for the past few days, almost all of which has been passive listening - and the album seems substantially varied without having any overly horrible tracks. I think I would have dug a slightly more introspective album from Trent - they tend to make for more subtlety. This seems to be a "funner" album than some of the previous ones (note that I am not even acknowledging with teeth here), and if this truly is going to be part one of a larger project, I think we can expect more atmosphere and subtlety in future chapters.
All conjecture and opinion though...