You can designate Elements as iPhoto's external editor, so when you Ctrl-click an image and select "Edit in external editor," it starts Elements and loads the photo for you. I use this with Elements 3 quite often to deal with product shots and crappy lighting situations that iPhoto's one-click Enhance can't deal with.
Adobe ought to make Bridge an alternate interface to iPhoto, working directly with iPhoto's directory and metadata structures. That would be a great way to encourage people to use it, because it wouldn't be any hassle either to try it or go back. With 1600 photos already in my iPhoto library, I wouldn't be hot to move all that to Bridge & re-tag it any time soon.