Just downloaded it today and am giving it a try as my default email client. I'm really liking how simple the application is, and that it's super familiar to what I'm used to on my iPhone. And since I use Google Apps for my email, I like that it takes about 10 seconds to add my account and be up and running. You should check it out (unless you don't use a Mac for some crazy reason beyond my control - come talk to me and we'll get you squared away).

Works with gmail and google apps accounts. Check it: http://www.sparrowmailapp.com/