People will complain anyway whenever there's change, but this isn't just a new interface; they've actually removed some functionality, some things that I used to use, and that blows.
I don't have thousands of friends like some people, but with over 100, I've got them divided up into lists. Folks from back home, people I know from where I live now, etc. You used to be able to pick which lists showed up on the left side by moving them "above the line". I could click each group in succession and do a quick checkup on the latest from each group. Now there's no line, and you have to click three times to get to all the lists (once to open the submenu, once to get "more" since it stupidly only shows the first two, then finally the list you want). Why?
Also, managing the lists themselves is a nightmare now. Just last night, I finally found the page where you can view a list of all friends (not just the ones with recent updates, or by group) under My Account at the top right, buried two levels down. Why?
They pump it as the new, "simpler" interface, but simpler does not equal better. I liked being able to customize things. I liked being able to choose which Applications showed up, not always view all of them. The bookmarks at the bottom are gone; I used those.
I think of the Yahoo home page, and how you can choose exactly which modules you want to see, and where they show up. Facebook could have done something like that, but with tighter restrictions to keep the uniform "look" they're obviously going for. We don't want it to turn into the monstrosity which is MySpace, but you don't just outright remove functionality that people use, and bury other stuff two levels down, and call it "better".