Not being a veteran of the first Xcom I launched into the adventure after trying the demo (not honors the finished product) and I am absolutely not disappointed! Despite its few flaws and bugs still present, the game will be improved over time with corrective patches. For more details about the game you can rely on positive tests (but goals) specialized sites (jeuxvideo.com, gamekult.com, etc.)
In any case it Xcom is a real success and if you like strategy and tactical games you will be served, especially since it is an almost non-existent in the current genre productions!