Up to this point, there haven't been very many 4K computer monitors to get too excited about. Some of the early models use lower quality panels, while others have janky issues pumping out 4K Ultra HD at 60Hz. The technology is maturing, however, as evidenced by Acer's XB280HK, a 28-inch gaming monitor with a 3840x2160 resolution and support for Nvidia's G-Sync technology.
Nvidia in October of last year unveiled its G-Sync monitor technology intended to reduce stutter, lag, tearing, and other unwanted effects associated with synching a monitor's refresh rate with the GPU. The company's goal is to integrate G-Sync into third-party monitors, though for a limited time, Nvidia is offering a G-Sync DIY upgrade kit that works with (and only with) Asus's 24-inch VG248QE display.