> Gmail is pretty much perfect

There isn't any room for improvement in Gmail? Really? It's still using the same basic design of every email client since forever (labels/mailboxes at the left, inbox shows a time-sorted list of messages, click through a message to read).

Meanwhile Sparrow showed what was possible if you sit down and at least tried to rethink the email interface -- with things like gestures, or by shifting towards streams rather than lists.