Depends on what you are looking for:
-Squeeze more endurance out of your batteries
-Better turns and altitude control
-Makes auto landings much easier
-Reduces possibilites of stalls
-One more sensor to tune
-One more part to break
IMHO the pitot results in a much better flight and I try to use it as much as possible, especially on big airframes for mapping that need maximum endurance. However, if I'm just testing something on a foamie I usually don't install it.