I needed the iDisk feature to share files over a distance. So, I had been planning to get .Mac already (had just been using the trial).
When I heard that the new e-mail addresses would be "me.com" I made it a priority to get it before the switch.
me.com just sounds to.... um.... childish???
It is a name that brings YouTube, FaceBook, and other teen sites to mind. It's a name that makes me think of a bunch of kids in a social network.
It is not something I would want on my outgoing messages to friends, family, or worse... Business acquaintances.
I don't actually plan to send messages from my MobileMe account. But, knowing that I could change my mind later, I wanted to have a more professional sounding domain attached to it. Though .mac is limited in appropriateness (only to a very minor degree), I cannot think of any instance where I would want a me.com address.