According to Walt at AllThingsD.com, the choice between MacBook Air and the ThinkPad largely comes down to whether you want Leopard or Windows XP (or Vista - ha!).
He states:
There are two more factors worth mentioning. I believe that both the Mac operating system and the software that comes with it are superior to the Windows operating system and built-in software offered on the ThinkPad. And the Mac isn’t susceptible to the vast majority of viruses and spyware, and doesn’t require third-party security software.
Also, the ThinkPad’s screen, when opened, stands significantly higher than the Mac’s, so it is less usable in a coach
