There's a related post on MSE here, and I encourage people to weight in there - I'm probably a lot more annoyed when I wrote it, a little later, and I don't see the point repeating it here.
As a long term user, and a moderator on SU, I'm pretty frustrated with the specific approach taken, and as a lot of folks pointed out, we got stuck with what's basically a beta theme. I'm frustrated, and actually a little angry with how this turned out, and I actually have been a fan of the new responsive layouts.
Having used MSE with the new theme, there's a few things our users are probably going to love. I currently use it in desktop view on my phone, and it just works, and as a mod, this is a very nice thing (The current theme is usable but less so). However as a whole, the theme is a disappointment.
Our theme though. Its... basically the generic theme, and the more I think about it, the less happy I am.
I'd ask you guys consider a black on white banner, more in line with the current theme (which lets us keep our bicoloured logo). The big issue I have with the current theme is, well... it quite literally dosen't seem to have anything to do with our site over the last near decade. We'd like to keep our identity.
Having looked through the existing themes, can we knock off what SF has, but with our site's blue over their dried LART residue red? or even what mathematics has, which is really close to what we have now.? I mean, this isn't going to take a massive amount of time, even compared to just throwing our name and logo on the beta/generic themes.