I will bet a vast majority of DJs here, including those that talk the talk, use very simple features of whatever DJ app they use. My guess it's probably limited to Play/Pause, some minor cueing, and tempo/pitch massaging. I'm guessing things like looping, filters, etc., are used less than 2-3% of the time by about the same amount of folks.
Some of the Traktor, and VDJ, and Serato features are great for the club DJ, but for those of us that do weddings, parties, sweet 16s, reunions, etc., they are fluff .. nice to have, but used very little.
I totally agree.
I have well over 300 functions in Rockit, that can be mapped to keyboards, controllers and skins. I actually use about 15 myself. I built all that stuff in, but I don't use it.
My favorite feature other the library stuff, is the Synch start -- load the same song into both main decks, right click on the crossfader, and choose the synch start. I built in a few ms delay, and the song sounds much fuller. You can FF or rewind either of the decks to get some more interesting effects such as reverb and echo.