Ahhh yes, the Pig is an instant classic. I also like Frogtone. I use the Pig in a rather unorthodox way. I only use it during rehearsal and use it very sparingly. Anyone who has ever done band rehearsal knows the cacophonous noise that it always is. In the midst of the fray, I whip out the Pig. Everything stops while they try to figure out what just happened. To quote the paragon of wisdom, the wicked witch, these things must be done "delicately". I suppose they will someday figure out it is me, but I'll enjoy the ride while it lasts.
Back on track, I usually build my own presets, but typically start with a preset and then let the tweaking begin. The beauty of the FX (in addition to das twiddlin' knobs und das blinkin' lights) is the sheer variety of sounds it can produce. So, I'm in the "love the presets" camp.