Do most use the double or is a single good enough? Doesn't it come down to line size or what? I'll use 15 to 17 pound FC most times.

Single is sufficient for me. I use 15 lb fluorocarbon most of the time with it. With the thicker diameters the double will add bulk to your knot, so I believe it is better with lighter lines. Correct me if I'm wrong.

I double it all, if I'm useing higher pound test it's for a reason, and sure don't want my weak spot to be my knot. Always give every knot a spritz of KVD L&L before cinching. Brian.

Single has never given me any trouble. I am knot sure how much stronger doubling can make it as long as yu tie it good.

I've never had a problem with single, double couldn't hurt though.

Single for me. 

Ditto

Never had a problem with a single either

Mike

Single has been the strongest, most consistent knot I've ever tied.  I've not personally had a reason to switch so I've not.  Another favorite part  of the knot for me is if you mess up and cross something wrong, or tie it wrong it will snap when you cinch it. 

Single always. I use the SD Jam knot 99% of the time. Palomar for the drop-shot. Really the only need for a double is when fishing large pound test for big game fish.

Single for Bass.