Gamersgate version is great, no need for third party launcher and the game launcher automatically checks for updates, allows you to enable/disable DLC and ingame you can buy it very easily too.
On a related note, I will buy nearly every single game release of Paradox if not for the gameplay, for the reason that there is NO DRM AT ALL in their games! I can't thank them enough for that.
Other game developers wouldn't have released a demo either since it isn't possible to just set the limit somewhere - Paradox, they just release a fully playable demo that you can even easily mod to be unlimited playable! And I am almost 100 % sure that the sales did NOT decrease for Paradox.