Generally I like it, BUT...
It's more simplistic now that the lines are removed from title bars and such. Those were a big part of the design because they made it stand out more and not look as simplistic. For example the white title bars look really white now, there's hardly any variation to them at all and it's a bit boring when they have no texture. Also the orange lines on the top right look too plain now without proper shading. I guess the site has just been redesigned to be more glossy, but there's not really enough contrast in the glossiness, it's hardly visible, and glossiness doesn't really suit GBAtemp since it's mostly a retro forum and glossiness is something new that everyone started doing since Vista...
If the lines were added back it would be pretty much perfect, those were a big part of the design in my opinion. Some parts of the design still have them, yet other parts look really plain after they were removed.
I also like the new features that were added with the new IPB and that everything is more smooth, the quick editor has more features and that the links on the top fade when you highlight them.