RE: Change of pace.
let's say you have an average current draw of 500 milliamps.
At 7.4V in, 5V out, the regulator will be dissipating about 1.2 watts ((7.4V-5V)*0.5A = 1.2 watts.
A 3S Lipo, 11.1V = (11.1-5)*0.5A = 3.05 watts. that would require some heatsinking for a TO-220 package. Stall a servo for a bit, the current goes up quite a bit, and power dissipation in the regulator goes right up with it.
A linear regulator like the LM7805 makes for nice quiet power (little electrical noise) but isn't very efficient at all.
You can find switching regulators (sometimes referred to as "BEC", or battery eliminator circuits) that are a lot more efficient at the expense of some power supply noise.
Castle makes a pretty neat little 10 amp regulator that I've had good luck with.