Well thanks for that! I really just want to communicate some of the more nuanced elements of the swinging. Granted, my conclusions on it being a design choice are chiefly made from my experience with the game, not from anyone at Insomniac. For instance, I did a "drug bust" and had to chase down the car as some of the goons got away, and you have to get a maintain a certain distance behind the car in order to close in on it and zip to the top & dispatch the remaining goons...if you had to do that with by building momentum and then maintaining the right amount of momentum, it wouldn't exactly be a fun experience, or rather, *as fun* as it could be.
There are a lot of options to move faster, but most gameplay videos didn't articulate that well. For instance, if you press X at the bottom of your swing, he'll vault forward with a speed boost, and you can increase your speed this way. If you press X at the top of your swing (the end) then you vault upwards, which gives you a good deal of altitude, enabling you to "vault" over big buildings. If you're over the top of a building, you can press L2 + R2, zip into it, and press X to immediately vault off the building into a swing. I found myself just vaulting over and around buildings to take shortcuts to locations instead of swinging around them and then running to the top of buildings. When you master these little nuances (it doesn't take long) you'll find yourself effortlessly navigating the city with great speed and it's so much fun.
So while the sandbox element of physics isn't there to "see what you can do", there is a lot of meat and potatoes there to experiment with and keep the traversal interesting and fun.
I played about 45 minutes and never once had the swinging stop. So long as I held R2, Spidey was swinging. I'd say that was likely either a controller issue or a freak occurrence. I could be wrong, but in my experience that didn't happen to me.