I think the museum USAirways787 is referring to is the CR Smith Aviation Museum, which is anything but boring, especially if you're interested in the history of American Airlines. The Flagship Knoxville DC-3 is reason enough to go for a visit. I try and make it each time I go to the Metroplex, I've probably been 20 times, and I still learn something new each time I go.
Additionally, the Frontiers of Flight Museum at Love Field is also quite nice, I was surprised at the amount of aircraft on display.
Dallas is lucky to have two high quality aviation museums.
With all of that said, nothing beats an early afternoon at Founders Plaza. Especially in the summer when you've got the winds out of the south, it's just a constant stream of traffic landing on 18R at DFW
. The new location is great for photography in the afternoon, but it's always fun to be out there.