Revised
There are a couple of quibbles, such as all of the soldiers across the world speaking with American accents, the odd camera glitch and a lack of diversity and number of maps, but these are minor blots on an otherwise perfect landscape.
Xcom is addictive as hell and if you try it once you'll keep coming back for more, trying to beat the game on the harder difficulty levels. I'd say this is a must for any lover of strategy games.
Edit: sadly, due to the gamebreaking bugs and lack of support and communication from Firaxis that has been the biggest feature of this game since it's release, I have had to revise my score downwards appropriately. Shame.