I'm not sure what it's like in the US, but here in Australia Mailbox's rating in the app store is a firm one-and-a-half stars. "Regular" people are finding out about Mailbox by browsing the "Top Apps" list, downloading it, getting confused by the queue, then leaving negative reviews.

The queue is certainly a novelty, and has generated some interest, but I wonder whether the Mailbox team couldn't have handled it differently.