I think it is super important to have honest discussion between developers, with as little flame possible about machines we are using.

I am using 5 yr old Macbook Air for development, it works well. I always imagined that I will use ThinkPad /w some Linux distribution in future. It is not trivial to use Linux on your laptop. While a lot of things will be faster, browser most likely will be slower and there will not be as many tools. What I would mostly miss is photography tools, Lightroom is essential for processing photos. I can't not do it.

Let me add one more thing to this fairly random post :). I think X1 is better then Macbooks and Airs at the moment, docking station makes a lot of difference.