I consider this to be a UX failure: visit page, adjust one slider, select something from a pop-up, re-adjust the same slider, and when I hit the Back button nothing happens. Click Back again, nothing happens. Long-click the Back button and see 20 or 25 entries for the site even though I never left the front page or obviously loaded new content.
If they dump the JS that obliterates my browser history that way, then I would agree that it is indeed slick.