Erm...can someone tell me what that "S > X" slider in the center is?
Other than that: it's kind of weird to have a controller that's about the same size as your handheld. Defeats the purpose of the handheld, if you ask me.
Unlike most, I'm a bit curious about the second D-pad (assuming the quality doesn't suck, obviously). Yes, it'd be awkward to use it in a 3D game, but the inverse also happens: 2D games where they assign some extra buttons on the analog stick's general up, down, left and right directions (for items, mostly). In this case, a D-pad is only slightly worse than individual keys, but still better than a controller.
Oh, and yeah...more portability and no drifting on this thingy. Small positives, but positives nonetheless.
Imagine using this to play fps games.
To be fair: I played through doom 1 and 2 entirely on keyboard. I admit it's not really a fair comparison since it lacked the need to aim up or down, but for that game this could be handy.