I think pacing is important, but I think there are much more meaningful relaxed moments they could have used instead, for example, the UC2 moment everyone loves so much, 'Where Am I?', it's slower paced, it's incredible visually, and it's enriching to the experience. I don't think the puzzles do that.I think if you are looking at some of them like traditional puzzles you'll be disappointed, but I like that they just force you to think and interact with the game in a slightly different way (even if it is really really easy). They offer nice calm moments and usually have gorgeous visuals. Also there were a few in Uncharted 3 that did require some thinking like the one where you have to look at the floor panels from a certain angle and then match them up with the tiles, the walking across the tiles in the right order, and the shadow puzzle. Again, not terribly hard, but they aren't meant to. They're offer just enough thought that it feels like you are using a different part of your brain than "run around and shoot things". But if you really like challenging puzzles I can see why you'd be disappointed.
Some of the larger, more Tomb Raider like ones are okay, the one from two where you pull down the dagger blades for example, I'm not sure that's a puzzle, but you understand what I mean, I hope.