Is it needed right now? No, but it is definitely the beginning of the future. We are very limited in how we can interact with our touchscreen devices, and up until this point it was literally just a 2D grid of points. Now we have a third dimension, with pressure sensitivity. In reality we are just at the very early stages in terms of things like haptic feedback, but 3D Touch is a very good start.
At the moment it is generally useful - I use quite a few homescreen shortcuts. Peek/Pop are nice but they don't really save that much time because the content isn't preloaded. Peeking on a URL usually ends up with me just popping into it because I don't want to hold my finger on the screen while I wait for it to load.