ummmmmm fun!!
and xp!!
and if possible, separate heroic completions from epic completions, so you can just do whatever quest you want to cap running quests once or grinding em on heroic and later on epic!
for gear matters... well, iirc the only thing i've run for gear was shroud, stopped me from tr'ing to hit 20 times to get the essence of cleansing, rest of stuff came with time, for the difference it makes, there's no point wasting time grinding it