I just started using imovie today after a Mavericks update last night, and so far I am seriously disappointed. To me, imovie is a whole new application, not an update by any means. I did CCC my hard drive before the Mavericks update, but I'd rather not jump back 3 OS to SL! Iphoto would not work after the Mavericks update, so I had to update that. So far, so good there. Imovie did not require an update, but I just downloaded all the updates and installed them. Shame on me.
My first impression is that the new imovie is nowhere near as intuitive or functional as the imovie '11 I was running previously.
*UPDATE*
I just read a few posts about Imovie 9.0.4 remaining in the app folder. I just checked mine and, sure enough, there are two versions of imovie in there. I fired it up and although it took a few minutes to access/organize the movie library again, it still works!
I will keep the new imovie, but definitely will not use it now, at least until I hear of some positive reviews on a functionality update.
Don't get me wrong, it's not that I don't want to update or upgrade, but if it ain't broke - don't fix it. Change for improvement's sake is one thing, but change just to change is something else. I guess that's why I'm only now updating from Snow Leopard.