Themed sets need to be pretty rare to be fun. So, sure, Mother's Day, Tax Day, Halloween, Turkeys... that's fine. But no Secretary Day, Arbor Day, World Series, Superbowl, Presidents Day, Mardi Gras, Final 4, Easter, etc.
Also, I think the best themed sets are the ones with a personal touch. So the Christmas one with all the Foghead phoned-in greetings is nice. Or Dave commenting on the Turkeys and what he liked about them. You gotta be involved!
The Giants set was probably the worst one ever.
Instead of using a whole 10@10 for a theme, why not bring back "my 3 songs"? Then you get to have fun with a theme but it's short enough not to ruin your day with a straight 45 minute set of dreck.