I'm a partner at one of the largest law firms in the world (top 10 or 15, by number of lawyers, depending on who's merged with whom recently).
There are many people here -- partners, associates, staff and IT -- who would love to switch to mac. I have a macintosh running along side my trusty xp machine on my desk, and I use entourage to get my corporate email. The IT staff has been very supportive, and have gotten approval to take mac support classes because so many lawyers have macs at home and need help with remote access, etc. I also understand that some of our marketing people are using macs full time to make brochures, etc.
It's just a matter of time.