Lots of stuff
They don't like 4e.
That's really not a big deal.
If you lost your friendship over that, all I can say is, wow.
That term if I recall was talking about the plans, salt and vaccum and a few others it touched on. Unfun was used a few times Skill checks and profession skill and out of combat skills being the ones I recall most. As I was told they were never used and an unfun drain on the game. So color my games unfun.
Yeah, one of the comments that really rankled me was something along the lines of "If you use craft or profession in your games, they must be really boring!"
Funny enough, almost immidiately after 4e came out, the one thing I saw most cry for homebrew was...craft rules