I have had success asking that my bags get rerouted so that I can get on an earlier flight and/or change to a different airport because of a delay, but...

A couple times this has caused my luggage to be lost for a day or two. Pretty much, I won't do this if connecting through ATL anymore, because this always seems to cause a problem.

I think I can even explain this: Once, I was on a flight to MCO when my office called and told me my Tuesday program was scrubbed, so I didn't need to be there until the next day. I quickly got off the plane, went to the gate, and they pulled my luggage, telling me to go to Carousel 1 to retrieve the bag. When I got to the Carousel, my bag was just coming up the belt. As soon as it hit the Carousel, a DL employee looked at the tag, picked the bag up, put it on a cart, and started to wheel away. I stopped him and explained the situation. He explained that he thought the bag was being mishandled and was rushing to get it on the plane before it took off. Bottom line, one person can promise you something about your bag, but if anyone looks at the tag and sees there is something out of the norm, they're going to - correctly - try to get your bag back to where the tag indicates it needs to be as quickly as possible.

I have had success in getting on the earlier flight but letting my baggage go on the later flight. I've done this a couple times when staying at a hotel near an airport. I get the extra sleep from having gotten to the destination early, and for a few bucks, the hotel will pick up the luggage while I sleep. Once, the GA didn't even ask about the luggage, and I dealt with it at my destination. The other time, when I went to the earlier plane's gate they did stop me over the luggage, but wound up letting me get on the earlier plane anyway when I explained it wasn't a problem arranging for the luggage to be picked up on my own.