Release date?

Just grabbed my pre-order copy, and having fantastic fun. I haven’t enjoyed a tower-defense game this much in a looong time (Ok i know GTB is not a normal tower defense game, but you get my drift…).
Anyway… apart from posting to say what a cool game, I have a few friends who are annoyingly on the fence about pre-ordering a beta game and wondered when the release date was? Any clues?