All depends on what you have ADW Launcher doing... Added animations, etc. that are above the normal launcher then yes its working harder and eating more battery. I still don't think it will be enough to really worry about in battery life.
I use it by default and its a great launcher with no battery issues whatsoever. The only way you'll know if it eats your battery is to give it a try. At worst, you'll just end up not using it and go back with stock or whatever you're using.