It's nice, everything's that little bit easier to read (presumably because 'white bg+black text' contrast better than 'white text+navy bg').
The VERY annoying thing I noticed straight away is that every post now takes up about twice as much screen real estate, since the signatures don't begin until the Join Date/Location/Posts/etc. info in the sidebar ends. On my gramp's 1280x1024 a two-line post takes up about 70-80% of the screen (dependent on sig size, amount of info on the left, etc.). I think it will look much better once I get home and back to 1080p ^_^
That's my only big complaint, all the rest is small stuff to easily adjust to, like the rep button being much smaller and out of the way, also half the signatures look a bit odd since they were designed for a dark background but that's easy enough to change
Edit: When tagging posts it says we can give it 5 tags, but when I put 5 tags it complains that's three too many.
Edit2: There's a random post in the What's New page (New Posts with a different name), which it says I don't have access to.
http://www.techist.com/forums/f123/article-first-build-help-234736/#post1832132
But enough negativity, thanks to all you admins and mods and cetera for all your hard work