Sometimes, specifically most notable in combat, my pipboy is unresponsive. I'm pretty sure this is a bug and not a (terrible) feature. I spam Tab button and I just stand there w/ my hand up my ass getting killed. After a few seconds, Pipboy finally pops up.

Seconded

Yes, and the same goes for weapons after reloading in combat... they take a few seconds before you can actually fire again and this is AFTER the gun has been reloaded.

Read my post in this thread i mentioned the pipboy also.

http://www.gamesas.com/index.php?/topic/1129725-this-next-attack-bug-is-still-here-from-fo3/

the bug has to do with single round reload weapons (Cowboy Repeater, .357 Magnum Revolver, Lever Action Shotgun, Grenade Launcher) any weapon you load one shell at a time has this random bug.

Not true. it happened to me with the 10 MM submachine gun when i was in vault 34