Gmail lets you use IMAP, which is as nice of an email transfer option as one could hope for in 2010. (http://www.dataliberation.org/google/gmail) You can even export your filters. - The article doesn't mention if the new Hotmail will support IMAP. The current one makes you have some strange "Windows Live" client as far as I know.

In this way I don't see it as Gmail imposing the switching cost (one could move away to lots of other providers or self-hosting).