[slippytoad]

I've been using my own Mac at work for the last 4 years, at 3 different companies (granted, one of them was my own startup). The caveat is you have to support yourself, which is fine by me. I get to use the environment I'm most comfortable in and I don't have to deal with crappy Windows updates, virus or Outlook headaches.

[cypherdog]

I'm nearly in the same boat. I've been at the same company for some time now and started bringing my personal macbook to work to code on. After awhile, I was so productive they bought me a one for work use. However in a 1000+ person company I'm the only one on a Mac, but I also have to do my own support.