I use Gmail, and form what I can see I love it, and to me it seems as it's even better than my current MSN E-mail, although it does have some ads but they aren't very noticible to me unless I want to look at them. :D
I don't use it. In fact I've blocked the entire domain causing any mail from GMail accounts to be bounced.
If someone wants to send me email, send it from an account where Google doesn't harvest the entire message content including my contact information.
I mainly use a fastmail.fm account, they dont have any adds. The storage is only 10 mb, which is not much but is enough for me. One thing i like about gmail is its auto forwarding service, no other free email service lets you do that.