Well I don't want to give much away, but it's like those misguided complaints about Uncharted 2 that there's too much globetrotting and that it's all over the map, only this time they're true!
So yes, it's not like Uncharted 2. In UC2 there's a distinct feeling that you're always going forward once you reach Nepal in chapter 5. In UC3 more than forward you're moving sideways, the game teleports you from location to location with its cut-scene swipes, the sense of progress is different yeah. It's that and the game starts at very slowly for the first few hours, and then ramps up like crazy and doesn't let go until the end. I just don't think it flows as nicely as UC2.
If you notice, every time I complain about something in UC3 I bring up UC2. UC3 is good on its own right, but inevitably for me the yardstick is its prequel.