Does it run OS X?
If not, it's nit a challenger!
Few people own computers to run OSes. Most people own computers to perform tasks. I know I don't care what OS is on my computer, as long as the tasks I want accomplished are possible.
For years, my OS of choice was Linux. Now it happens to be OS X because Apple suddenly made laptops that interested me and were the best choice for what I wanted. Frankly, any Unix Operating System does whatever I need to get down on a computer.
Lenovo's X1 (whatever Coldmack says, hello, the MBP is the same Intel CPU+GPU combo... but at least the X1 has a IPS display, which is more than can be said about Apple laptops) has some good things going for it. It lacks a proper GPU for my taste, but then again, so will the next MBA for all we know (and we know thanks to the 13" MBP).