Everyone I've talked to agree that there are better tools for the job, ranging from the firearm itself, to the 5.56mm Nato round.
How embarassing to be doing drill and smack the handguard right off your rifle. (New handguards I might add)
I know it strikes a nerve with many, especially those who buy AR's because they look all tacticool and you can put 500 pounds of tacky accessories on them, but I'm only speaking from my experience.
This is all to say that I don't want one for the tacticoolness

however again, much better tools for the job.