Gmail deffinately wins hands down for me. I've been using it for well over 2 years and can safely say it is the best email service I've ever used, and I've used a lot.
Gmail has excellent spam filters compared to some other popular free email services, I very rarely have to remove spam from my inbox. Also, very generous space allowances, so no problems there.
As always, Gmail invites are avaliable for anyone who wants one. Just PM me with an email addy to send it to.