PRAISE THE EMPEROR
Here I kind of disagree. In interface? Yup. Openness? Nope. The game is extremely streamlined, and while that makes gameplay a bit faster, it's not as nuanced. Research appears to be just kind of linear, for example, and the overall unfolding of the game and tactics is a lot different. You don't choose the armament of your interceptors for example, don't have to worry about buying ammunition and other supplies, don't have to worry about base defence, preventing alien bases from being built / attacking / starving out alien bases, etc. The expansion promises to fix a lot of that, however... And I'm not denying the game is good. It's damn good. I just think that at release the game wasn't as good as the old one.
The original XCom was a horrible broken, bug-ridden unbalanced mess. It's practically a miracle that the game is playable at all.