The gamepad lags incredibly badly (at worst, it freezes for up to a second at a time). It only lags for my two physical games, Smash Bros and Mario Kart. Netflix and Virtual Console games do not seem to lag at all, maybe because they're slower paced than Smash and Mario Kart? Nintendo says I can send it in to be fixed for $100, but I'd rather not. Cleaning under the screen (toothbrush under the edges) and on the screen helps some, but not entirely.
Here's a link to it that better shows what I'm talking about: