It's that time of year again: Lenovo whips out some impossibly thin and light laptop. Last CES it was a 1.7-pound notebook, and this year it's the Yoga 900s, a half-inch-thick, 2.2-pound machine that Lenovo claims is the world's thinnest convertible laptop. Indeed, I had a chance to handle it in person and it really is absurdly, impressively thin and light. (I know, we always say that. But still.) Before you get too excited, though, it appears that the 12-inch Yoga 900s is the spiritual successor to a machine that ... we didn't like very much. That would be last year's Yoga 3 Pro, a super-slim model that ultimately got a lukewarm review on account of its sluggish performance and mediocre battery life.