We are flying Delta for the first time in September. I booked our tickets at the end of March. We are taking a 50 minute flight from Indy to Cincy, and then a 2 hour flight from Cincy to Orlando. So far, they have changed the schedule on us 6-7 times. Most of these have been very minor (equipment change, or the first flight has changed carriers like 3 times). Even those minor changes, however, have resulted in us losing the seats we picked (a big deal to me since our layover is very short and I want to be as close to the front as possible). I just keep checking every week or so and calling to reassign seats-a pain, but no big deal. They changed our return flights on NWA a few weeks ago and those were a bigger deal. I tried to call and see about being assigned different flights since we made the minimum layover time by one minute. They wouldn't let me (but I didn't push too hard!). In this case the constant changes has worked in my favor a little, since their has been another more recent change and the layover is a little longer again.
We still have 85 days til we fly, and I am planning for there to be many more changes still to come. I wouldn't say I've been impressed with Delta, but they haven't been terrible either. If the price is best by far, I'd risk it. HTH!