With regards to all of the comments about the ThinkPad being ugly, you have to appreciate the important facts;
Apple design: form over function
IBM design: function over form
There's no denying that nearly all of Apple's products suffer in terms of functionality just so they can look pretty & the MBA is the prime example of this. Apple are more concerned with their products being visually appealing than highly functional, because this is their market; pretentious style-concious people who are more concerned with their stylish image than whether their computer is actually any use as a computer. In this regard, Apple pull it off very well.
ThinkPads OTOH have retained the same visual design since the very beginning of the range back in 1992. Why? Because it's a fscking solid design, which allows the ultimate functionality in the form factor & makes extremely strong/durable machines (that's the reason they've been used on the spacestation(s) for so long!). ThinkPads are targetted at the business sector; people who want a solid machine that also looks professional*. In this regard, IBM/Lenovo pull it off perfectly.
(* 'stylish' is not the same as 'professional'. Prada stilletos are 'stylish' but black leather suit shoes are 'professional')
Yes, these two machines are in some regards direct competitors, but in other respects they are not. Yes, they are targetted towards people who want a full screen & keyboard in a thin & light form factor, but there is a clear divide between who will buy each one. The MBA is targetted towards the "professors, writers, journalists" (to quote a previous post) whereas the ThinkPad is targetted towards your traditional suit & tie business man.