I've spent a few hours playing it, and although some of the stuff seems interesting (although I bet after a few weeks after release, no one will play the extra game modes) I just don't get the point of CS:GO. It doesn't do much new that the old CS games didn't do themselves, if they are going to just copy and paste CSS then the least they could do is take 1 aspect of the game and modernize it.
At least with each of the new CoD games they release each year they have a new singleplayer story, they add new weapons and customization, new types of combat/maps etc, even though they just copy the same engine. I've never been much of a big CS player, but I just don't 'get' what CS:GO is meant to be bringing to the table.