Tynan, the head dev., has not talked about a specific full release date yet as far as I know. It's available on steam atm and you can of course buy it at: Rimworld. I bought it months ago and have over 1000+ hours easily in the game. The replay-ability is enormous. The forums on the official website have loads of mods which are easy to install/add.
In my opinion it's worth the money for sure. The soundstrack is amazing and the amount of "Oh fuck,did that just happen moments" are endless. Check out the Rimworld category on twitch, if you have doubts. Tynan frequents many twitch channels and from my experience is willing to listen to feedback and answer questions.
Hope that answers your question @GnomishViking