The thinkpad X-series are made of carbon fiber[1] and you get the legendary keyboard. The Thinkpad keyboards are IMHO the next best alternative to mechanical keyboards.
The current X-series keyboards are probably better described as "infamous" than "legendary". Not that they're necessarily bad, but no one who would ever use the phrase "legendary Thinkpad keyboard" was happy to see them go with yet another crappy chiclet Macbook clone.
Have any of the critics you refer to here actually used the current keyboards? For over several months? If that is even the case, they are probably those who prefer form over function, because the current keyboards are objectively no worse than the classical one and even better on certain aspects. The current keyboards have similar tactile feedback measured, even bigger touch space, better design for maintenance, and greater endurance against grease and dirt.
[1] http://shop.lenovo.com/us/en/laptops/thinkpad/x-series/x1-ca...