Wow, highly anticipated, and it doesn't disappoint. For those that played the original some 15 years ago, they remained true to the core principles, such that waves of nostalgia still come back through the updated visuals and streamlined mechanics. For those that are new to XCom this is the pen-ultimate turn-based squad-tactic strategy game of all time.
Some have written of the appeal of peril, and they are correct to a certain extent - there's also a sense of great achievement when you learn something though. a particular mechanic, or how the (simulated) world works, and start playing it to your advantage.
Either way, XCom is an addictive and challenging experience. Overall, an amazing, awesome title.
By the way, after many Ironman-Impossible attempts, this is completely cool.