last month my flight from Detroit to BWI resulted in a bag coming out 35 minutes after I landed. Granted it's BWI where everything is somewhat related to Baltimore and its usual backwardly characteristics, I still expected the 20 minutes gurantee to hold up. So, I sent an email only to be replied back saying that it was indeed 20 minutes. I replied back saying to check their "flight information and bag arrival info" one more time. They said I was right and gave me miles.
BWI still blows. But Delta is working out OK for me.