I've been using my ECB for about a year, smoking 4-5 times per month. I only put water in my water pan, and never anything else. Rather than using the water as a temperature stabilizer, I use it to keep my meat moist, and also to get more smoke onto my meat.
I live in an area where temps rarely dip below freezing, so my experience might be a bit different from others, but I swear by my water pan. Myron Mixon uses a water smoker, and Meathead and Greg Blonder at amazingribs.com explain the science of how water vapor will land more smoke onto your meat. It'll also probably lengthen a stall, though. Either way, those are guys who seem to know what they're doing.
Just my two yen.