I swtiched to Gmail at the end of last year, and am loving it. We did the same at work and we have a much better mail system for much cheaper. The filtering and labeling system is both powerful and easy to use, go learn some Tricks to improve your Gmail experience at Coen Jacobs
Besides it’s flexibility and being available via the web, the filters and labels are the greatest features in Gmail. The greatest thing about it, is that they work together like a charm.