Its user interface, both old and new, is lousy. For instance, the inbox listing only uses about two thirds of the vertical pixels available on my monitor to list messages (for those of you in Rio Linda, the purpose of an inbox listing is to list the messages in the inbox — the more the better).
I also use indiatimes.com for semi-junk. It's cool in that the URL isn't an obvious web mail account. The ads are sometimes interesting.
I use Gmail for my main account. It has a spam filter to die for. And it's just ... easy.
One “account” I use is mailinator.com. It is a completely open account, so anyone can just check anyone else’s email without passwords, but it is great for making up a temporary email account name to log onto a site. For example if you need an email to read a full article, just make up a mailinator name, give it, look for any confirmation email there and then forget you ever had the account. The also keep a pool of other domain names for those sites than reject mailinator addresses.
And if you use Firefox with Gmail SMTP you will never see any ads.