Soft 75 looks the best, if slightly dark. Soft 100 looks blurred on the tower details, I think I prfer the ticker fog of war too. No HDR looks pretty flat although it is the cleaner look.
Extend the beta, but beware making it an overly long protracted affair. Eventually i would like to be playing the finished game that I ordered, umm, ages ago! :) I do think that elemental is the sort of game that can benefit alot from player input, there isn't much like it on the market right now and you are attempting to innvoate with it. Gor for it.