Cool looks of optics aside...switching back to iron sights was one of the most liberating and fun things I've done in a while. No worries about if the optic is still zero'd, if your batteries are ok, if it's going to get shaken to death, etc...
The only issue I had was shooting in a really dark environment at longer range (and lights help with that...having a buddy spot with the light from cover is even better
).