I have Powerbeats wireless 2 headphones and have no perceptible delay. I wouldn't be able to tolerate a half second delay.
I see here a lot of people talking about delays and how $2 wired earphones solve the problem. So I get people buy cheap and wants quality with their new iPhones. Cheap earphones with or without wire are always crap, the sound is horrible and the quality follows. It might be the reason of the delays: cheap stuff