In response to some of the critiques (and a bit of my own):
The black bar doesn't really stick out all that much when ACTUALLY viewing gmail in the preview theme. I find it very easy to ignore. Some people have complained about the gray on white. In my case the coloring is MUCH nicer on my eyes than the old theme. As far as the text being too light, it really hasn't lightened much and is still very readable on my screen, although darkening the operations links would help some. The UI in general is a bit more drab but I imagine Google is expecting (hoping?) that people will spend a lot of time using this design (remember, they're using similar design elements on Google+) and want to improve scan-ability and reduce eyestrain. The extra padding also helps with that. As for their operations buttons, I'm really impressed that they went this route. The use of "current internet style standard" icons instead of text shows that they're trying to condense and get the UI out of the way and make a cleaner interface. I also really like the extra spacing; that makes things much easier to read (even in condensed). Good work, Google.
As for things I don't like: Let's extend the message container all the way to the right edge, please. There's already padding between the date and the container edge and having those rows stop short just looks strange. I know what you're thinking, "but if we do that, the pagination links will be right at the edge!"...so right-align the older/newer buttons with the date display instead of the end of the row...easy stuff.
Did anyone else notice that the "highlight" colors used throughout are very close the Google logo colors...unlike the original which used more Microsoft-standard colors?