I was (with some effort) able to install OS X, snow leopard, as well as the dev tools onto my IBM X61 and have had no issues with it or developing IPhone apps on it. I have the OS fully functioning. Note: I bought a retail copy of Snow Leopard for my project.
Why? I had more time than money. If I had to choose again and I had the $1500 beans (+tax, + whatever) to buy a mac book pro I would have as it certainly wasn't 'simple'. But I didn't.
But now that I have done it, I have an immensely cool IBM MacBook :) and am quite proud of the accomplishment. I also learned an awful lot in the process. Was it hell? Yes.. Was it worth it? Yes...
Hope that helps!
