Whats the easiest way to migrate from SBS to Exchange 07?

I need to migrate from a small business server to a new box that will be running server 08 64bit with exchange 07. Before I go figuring it out on my own, I figured I might as well test out the fluther community, so anyone done this before? What’s the best and easiest way? Obviously, if its harder but will guarantee no data loss that would be better.