I dumped Sparrow when Google bought them. The bare minimum will be done on the app to keep is sellable. They won't do anything to make it better unless Google replaces their app with Sparrow....or somehow makes the two better.
Personally I am tired of the tripe about "reinventing" email. It's like reinventing breathing, or air. All they end up doing is making a different sort of ogranization structure....which I need less of. I need two things.
the ability to search easily and quickly for past, present emails (I won't rule out future emails but I don't think the Stargate Program has that nailed yet).
And tag, flag or star (whatever) an important email for even faster reference.
Everything else is just nice. When I was using Gmail I never did folders, stars, smilies, or however else organizational methods were pushed. I just needed to search and sift information. Gmail excelled at that....and iCloud isn't too bad either.
I just lost it with Google when they integrated EVERYTHING into my Gmail inbox. Then they changed the UI for Gmail making everything 400 times harder to find (still have troulbe finding the New Email button).
I moved to iCloud solely. Search isn't bad. It is hard on the iphone since it is mixed results to searching the server based archives, but otherwise pretty good.
Sparrow is nice. It hasn't made me change my mind about replacing the native app. It has some nicely implemented features but nothing that justify the price. Epspiecally since they haven't gotten the badge issue resolved....and I am not buying their excuse. there are other mail apps that have succeeded without charging a subscription fee.