Althogh Sparrow supports non-GMail protocols, it really is primarily for GMail. I use a standard IMAP-mail provider (folders, not tags), and to me Sparrow added

Althogh Sparrow supports non-GMail protocols, it really is primarily for GMail. I use a standard IMAP-mail provider (folders, not tags), and to me Sparrow added very little over what I had with Apple Mail. (Conversly, when I used GMail, it didn’t work that well with Apple Mail.)