CS:G.O. is very different from source and 1.6. I can tell you that much.
The buy menu is very different. Takes some time to get accustomed to.
There is recoil in global offensive. You can see the bullets flying differently, so that also takes some time to get used to (understand how they work).
I am not sure if the game will grow on me, i guess it can only get better from here given this is still a beta. I like the maps, well detailed and nice to look at