Phoronix published a review on the 4K Ultra HD Graphics Card Testing On Ubuntu 14.04 LTS
A quote from the article:
With the release of Ubuntu 14.04 LTS "Trusty Tahr" right around the corner we have out today some new benchmarks of various AMD Radeon and NVIDIA GeForce graphics cards when testing them with the latest Linux GPU drivers on Ubuntu 14.04 at 4K (3840 x 2160).4K Ultra HD Graphics Card Testing On Ubuntu 14.04 LTS @ Phoronix