Probably not much. I have multiple email accounts. Yahoo, Earthlink, Gmail, Work etc. I use my gmail account not for the storage but for the spam filters. Yahoo's are pretty bad but getting better. An you have to pay for POP access. For Earthlink I use a white list but it's a pain to manage. Work has very few issues but it's my work acocunt. Since I own the mpolino domain, I can forward it to any email service I want. This makes it easy to change services but keep an @mpolino.com email address.
I've blogged before that I don't like gmail's interface. While implementing Getting Things Done, I've cleaned up my email and decided on Outlook as my single point email box. Everything now forwards to Outlook. I have good backups for my local archive and solid webmail access via Outlook. I don't like being tied to a single provider. Too often one provider leapfrogs another in feature and I want to try it. So what would it take to move me from gmail? Not much. Just solid spam filters. I'm looking forward to trying the new Hotmail beta.