It's not really integrated because you have to have SimpLESS running in the background whenever you're working on a project - it's not a major hassle, but I noticed a similar friction when working with LESS.app in a project. I could edit almost everything in my text editor and see the results on the page, but would have to leave the editor to start LESS.app when I wanted to tweak the style. Only had to do it once, but it didn't feel like an efficient, integrated workflow.