I remember switching to Gmail and being in awe of its sheer awesomeness. It just felt... right, if you know what I mean. It's hard to put a finger on it, but the old Yahoo and Hotmail systems just felt clunky. I suppose that's why so many people have made the switch to Gmail already.
But it looks like Yahoo still has some tricks up its sleeve, because I logged in the other day to verify some account I had to set up for some reason, and was asked nicely if I wanted to try the new Yahoo mail beta. Why not, I asked myself. Not like I care about this account anyway. Suddenly there was a guy in a purple suit walking around on my screen giving me a "tour" of the very-different-and-very-ajaxy Yahoo mail beta. And I have to admit, I'm pretty impressed. They've come out of the gate with a lot of features and a lot of help available to make sure you get the most out of them.
It's got an integrated RSS reader, should you choose to use it, and also includes Calendar and Notepad applications. Overall, it looks like they ripped off all the best parts of Gmail, but polished them up and added in some of the more glaringly-absent features. For instance, the free Intellisync program to sync up your Yahoo calendar with your PDA, Outlook, etc.
I'm certainly not leaving Gmail anytime soon, but that's mostly because changing email addresses is a pain. If I was choosing my first email provider, though, I'd be seriously considering Yahoo right now.