While I don't think it's terribly bad I still prefer the old one, the new one looks too... simplified for me. As I said there, this might be good for mobile phone users but it looks a bit too blank now for me on my 1920x1080 screen.
For the user it's less features than before (voting, rep system are gone) but IIRC someone of the site staff said that it's easier to administrate, so I guess that was their main reason to change it.
I didn't think it was too much clutter before, personally when it comes to computer programs and related things, I prefer many options and menus to be visible and just one click away instead of having to click myself through several sub-menus just so that the main program looks more streamlined. Example Firefox: I instantly reverted back to the old style when they hid away all menus and even the bookmark menu bar which I use a lot into a single button with the introduction of FF4.