They can't run OS X as well as Apple laptops can, unfortunately. Lenovo isn't using EFI firmware yet, and even then, there'll always be a bunch of little bits of hardware that are a little bit different than what's in Apple's portables.

I'd probably purchase in a heartbeat if a current Lenovo T, R or X were offered running Leopard fully supported. They're definitely not bad machines under Windows though, and I find Windows Vista on mine to be even enjoyable.