Looks like it's great for building the things the authors thought you might want to build. Just like every other "SuperMagic" framework, I suspect there's a lot of pain to be had once you step just a little outside of what it expects you to do with it. We've all re-written Django inside of Django at least once, and thus have been burned by this sort of thing before. Personally, I think I'll wait to see some big proje…
As for big projects, well, Foursquare is written in Lift.