So for the first ten levels or so I was blissfully content with FO4's performance. It seems very stable. The AI is vastly improved. NPC's are behaving well. I got a few bugs but, you know, whatever.
But the load times have grown longer and longer, despite the game being played on a fairly powerful rig. But the worst thing I'm getting is this HORRIFIC delay when switching weapons. I went into the Four Leaf Fishpacking Plant and encountered a Legendary ghoul. I ran away and zoned back outside. When I finally arrived I switched to my shotgun. It didn't come to hand. I was stuck, waiting for it, without being able to sprint or run, as I fled from the Legendary ghoul and his four friends (who materialized out of thin air). I was "rescued" by a run in with a band of raiders ambushing a scavenger... at the South Boston Police Dept, which is nearly five blocks away. As I ducked around a building the game finally relented and allowed me to have my shotgun... which I no longer needed.
Folks have said that switching weapons in the pip boy doesn't have the same problem. I'm getting it no matter what I do and I'm tempted to stop playing FO4 until it's fixed.
*sigh*
At least there are no backward flying supermutants....