Asus Zenbook Primes seem to be a very high quality Ultrabook series as well (be wary of the differences between 32VD/32A and 31 models)
Also, the Zenbook Primes mostly have 1920x1080 resolutions. While the X1 Carbon was upgraded from a pitiful 1366x768 to a 1600x900 resolution, it's a shame they are still a bit backwards on that. I'm wondering what people think on the 1600x900 vs. 1920x1080 issue and how much of a difference it makes.