During any medium to large scale conflict, I can't open my menus, switch weapons or use VATS. Any one of these functions takes anywhere from 10 to 30 seconds to perform, by which time I'm dead.
I noticed this even early on in the game at the correctional facility. There are only like 6 guys or so that come rushing at you once inside where the leader is. If you have your +guns skill up and the correct weapon out, it's no problem, but playing the game I have been, with my +guns skill currently at a 2... I used explosives, and moving around and switching between types of weapons and pulling up Pipboy were annoyingly slow.