I use Sparrow for iPhone with Gmail.
Sometimes it confuses me because the unread count for some of my labels doesn't match with the one shown in the Google Mail app (it's lower, presumably because Sparrow doesn't download all mails).
The thing is, that I know the expected unread counts of most labels, and if they differ from the official app, I can't quickly see whether there is something new in or not.
I think for this to work correctly, Sparrow would have to download all mails, or update the unread mail counts from the server instead of the mails it already has on the device.
Is that possible?