GMAIL from day one, got the beta invites in the begin stages where only private corporations got them
I use gmail for pretty much everything except professional correspondance. For that, I use my university's address.
how is it unreliable? I've used gmail every day and it seems to work fine. but I'm sure we all have different experiences. if you want one that's not owned by a big corporation, then you can start your own site and use that.
Mostly gmail, I have hotmail accounts and a yahoo account but rarely check them. Most email accounts are forwarded to gmail.