Yes Ashery, I've played original XCOM with the Util. I've also spent many hours on Firaxis' version of XCOM which I enjoyed, especially with the DLCs that came out which made it more "complete". I've also played the whole UFO trilogy (by ALTAR Interactive) which I also enjoyed. I've put some time on Extraterrestrials too but I didn't get to finish it. I've yet to try Xenonauts though and that's bugging me.
I'm not willing to pay 20$ though without knowing if I will like the game or not. I appreciate the effort of bringing a polished original xcom edition by the devs, but I don't know them, I can't be sure of their work. I've spent money on pre-orders but only when I was sure of the dev team from previous experience. That's why a demo is needed, or at least another incentive to pre-order the game...