I've had invisalign for almost 2 years now, and I have to admit it works. But spare yourself the agony, and go for braces, it'll save you atleast $1000, if not more. Brace's will guarantee a straighter alignment as well.
What I find a pain in the behind is remembering to put Invisalign back on after I eat and after brushing my teeth. They can get pretty yellowed and dirty, who want's to keep sticking it back their mouth? Not to mention, it's a complete hassle to visit my dentist every OTHER week. I'm pretty sure he has no idea what he's doing either.
Obviously, not many others agree with my feelings about invisalign. But hey I'm speaking from my personal experience. And I can't wait until I'm rid of this plastic junk.