I've seen some good builds on that page but I've also seen some seriously WTF ones as well.
I saw one a couple weeks ago where the guy had so much shit on there that he'd have to hunt for the trigger. It had a high mount scope with a red dot on top of that, flashlight, laser, iron sights on the rail, offset iron sights, a foregrip, and I swear to God, a fucking bayonet - AND PEOPLE WERE COMPLIMENTING HIM ON IT!!!
My ARs? A red dot, iron sights and a quick detachable sling. My house AR has a flashlight in addition to that.
Keep it simple, stupid.