You know Reach is for casuals when the head shot hit boxes for the sniper are like a mile wide!! (Exaggeration for the win)
You know Reach is for casuals when emptying a clip into somebody is less effective than double melee.
You know Reach is for casuals when you get online and your team wont speak to you at all.
You know Reach is for casuals when you can fly over map geometry whenever you want.
Any other ones? =)