The "about this community" sidebar is gone, so basically, all your rules and links and guidelines are missing. I think this implies that it'll have to be re-done as a message and pinned, meaning you lose the ability to pin the contest. grr. (update: technically, no. It's now hidden behind an icon (the circle around i) up in the upper left corner on the logo image. So in practice, nobody will ever see it ever again)
The left sidebar with the categories is now hidden below a drop-down menu you have to click. The practical side effect of that is that nobody will, so they're effectively gone, too.
For reasons I don't remotely understand, they've now colored the category link, so it now draws the eye and makes it grab your attention away from, well, other things like the author, the message or the image. this is incredibly stupid.
IMHO, whoever did this design is an idiot who doesn't run any communities of any size on G+.
I'm sticking with classic G+ for now. This messes with the system in bad ways, IMHO.