Reply to S4/S2 for a paid gig?

Who here uses their strictly uses S4 or S2 for a professional paid gig? I know most professional would also have a backup device but i'm mainly interested to see how many DJs out there uses the S4/S2 primarily on their gigs no matter what genre of music they play.

I'm curious to know the quality and its durability on a working environment and expose to different kinds of elements.

If you do use it do you have any complaints?