Some good features -- tabs, searches, gmail-like thread displays. It's a good user experience, better than Mail BUT beware, the spam filtering is crude -- nowhere near as effective as Spamsieve. It is particularly poor at learning spam matches, even using the recommended routines

Also, the company culture is a bit nauseous, impersonal and hiding behind the world's worst feedback forum which isn't a proper forum at all -- you cannot see what is being discussed by others, merely search for issues. I dislike dealing with this company so much that I might go back to the imperfections of Mail which does at least handle spam well.

The advantage of small, independent developers is (usually) that they are accessible and talk to you. Not this lot.