All good points....
I know why the cap is there, it's definitely not the end of the world.....
I dunno, my next statement is completely subjective and of course prone to vicious ridicule, but I detest any seemingly arbitrary barrier to progression.
Like, killing a boss in an instance? He's dead, won't be back for a week, that "feels" fine.
Killing a boss again in LFR and not getting anything because I already killed him? More annoying, but I knew that going in. The message that shows what you WOULD HAVE gotten if you were loot eligible is a hilarious kick in the balls, but it made me laugh.
Having quest rewards reduced / changed or reducing the prize of completing a dungeon or a raid because of an arbitrary cap? Again, I know why it's there, but it's so...
Inelegant.