I think the general source of frustration with Sparrow's acquisition is the feeling that something beautiful just got end-of-lifed. And of course that this is just the latest in a line of could-have-beens like PushPopPress, Tweetie, etc.

And I had a similar train of thought as the OP: "I wish Apple could make the App Store even more profitable, so we can have more great independent developers like Marco and TapTapTap that continue to make great apps without being gobbled up by large companies eager to put talent into unrelated areas."

I don't know if it's possible, and of course no one can fault Sparrow for cashing out. But there it is.