I've had my K1 for a few days and I really like it. I've changed the launcher and had to upgrade the keyboard but otherwise I'm happy. I tried playing an HD video today on the gallery video player and it kept lagging (as well as the arcsoft). Is there a video app that anyone likes that can handle HD video?
Try running the MX Video Player app, which is free from the Android Market. If you decide to try it, you'll also want to download the "MX Video Player Codec (ARMv7)".