A similar discussion from a few years ago:
Payload Optimization Flight
Some good post from Delta insiders.
I have heard it a few times on some relatively short flights (<1,000 miles). All depends on the winds, loads, cargo, etc.
The issue with gate checking is the way weights are calculated. Passenger + cabin baggage has a different weight calculation than passenger + checked baggage. Here is a news article with some details (recent average weight increases from 2005):
http://articles.orlandosentinel.com/...ter-of-gravity