I'm interested in starting to edit videos and I'm looking for a good video editing application. It shouldn't be too complicated but one should be able to do advanced stuff with it too. I currently got iMovie but it's too simple for me.
I can recommend Final Cut Express and if you want it real pro - Final Cut Pro. Note that a major new Final Cut version is nearly out - probably with the MacOS X Lion. Also note that some price drop is expected for both products, probably you should wait a month.
IMHO with imovie you can achieve NICE results, especially, when you starting to edit.
iMovie has several very nice features (some are not obvious at the first look), and probably you still do not discover them all.
Using professional applications like FinalCut and so on, i'm not recommending for someone who starting to edit. But, opinions are like slaps - they're always different. :)
Maybe, can you be more exact - what feature you missing from iMovie?
iMovie is a great piece of software that can do almost everything that the average user wants it to do.
Without typing out a long droning answer, I would absolutely recommend Final Cut Express. Changing from iMovie to FCE and FCP for me (a while back) wasn't very difficult. The application is brilliant and you'll have a lot of new features to play with, as well as the ability to use plugins, and much more.
Final Cut X was announced and will likely be released soon, though, so keep an eye out for that.