It's fucking lame and one of my biggest complaints with the title. Now, if installation at each act was the solution to allow seamless play throughout each act, start to finish, I would be okay with it, but it isn't. You still have to load each and every time you enter a new area, before each cutscene, and often several times during what should be intense action sequences. It absolutely harms the immersion.
What makes it more egregious is that other titles are capable of pulling of similar sequences without chopping up the action. Imagine the jeep chase in Uncharted if after every third enemy you killed, the game needed to load. But guess what, it's a one shot chase, start to finish. Oh, and it's probably one of the best graphical sequences on consoles to date.
Loading sucks. It should be minimized. And if installs are going to be used as the method to curtail frequent loads, then they should, you know, curtail frequent loads.