Hey, so I'm trying it the default beta (I assume that's the one you wanted), so can I give a little feedback here? I mean, I assume that's what you bothered for, and I am good at it. Also, the general feedback topic is locked, so yeah...
The new interface is pretty slick, and I like that notifications don't up and vanish as soon as you click them (there is a list that doesn't go away), and messages are easier to see too. Easier shortcuts to search for posts by a user, etc. All of that is great.
But I have a few issues. Is there a way to maybe go to the dark gray as the old default? White is always rather... plain for forums. I always think darker adds something to forums, and I doubt I'm in the minority here either.
And I think my biggest gripe, personally is, natures are removed in posts. It might not be much to some, but I've always had so much fun finding and viewing those, even back when I only lurked. Why get rid of those? Also, you can't actually see likes on posts anymore either. Miss those too.
There's more good than bad, but hey, might as well give some feedback, since you granted me the opportunity to try it. But if I'm being honest, I really do prefer the original a lot more.