We flew Dublin to MCO via Atlanta in August. We cleared customs and immigration in Dublin and bags were tagged to MCO.
Delta were fine, food was pretty dire on the way there but a bit better on return journey and we were delayed an hour in Atlanta with the Atlanta to MCO flight also taking longer than scheduled due to weather en route, in flight entertainment was pretty good.
My big complaint about Delta was that on the way from Atlanta to MCO they started putting all wheeled cabin baggage in the hold. As we had kids with us we had one rucksack and 4 wheeled bags so we arrived in MCO with the one rucksack for 5 of us,no change of clothing or anything like that if the luggage had gone astray. They said to take out anything valuable but we had nowhere to put anything else and no time to think of all the little things that we did not want put in the hold. I ended up arriving in MCO carrying my 'planning folder', with our tickets and emails in it, by hand.
Fortunately all the bags turned up with the rest of the luggage but they were a bit battered looking and I have no idea why they did this as when we boarded the plane there was space in the overhead locker above our seats.
I would still use Delta again for the right price but would be more prepared for this possibility another time.
this is one of the reasons i hate delta - this happens often within the US...when you're on domestic flights...
the cabin crew and the ground agents love to make up their own rules..
it's happened to us many times...
the worst time was when i was flying with DD from JFK to MCO - on the way to her audition at WDW, when the cabin crew made up a rule that she had to gate check her guitar (not true) and they went further to claim that it was an FAA rule (lie lie lie)....
and they assured us it would be waiting for us at the door when we landed (another lie)....but then when we landed, and we came to the door they said, "oh, sorry, only strollers are brought to the door, you'll have to go to baggage claim - special services to get the guitar"..
so when we got to baggage claim and told them the crew had forced us to gate check the guitar the people there had heart failure, said the crew shouldn't have done that.
that the guitar is permitted on the plane - which i knew as i'd checked it beforehand..
and then one of them went running in search of the guitar, only to be met by one of the luggage crew running in the opposite direction carrying the guitar, freaking out that the cabin crew had gate checked it..
luckily, the guitar survived and she was able to audition (successfully), but it was a nightmare for her at the time...
and that is very typical delta - they are known for making up their own rules that way...
DD encountered the same thing this summer on her domestic flights across the US to get to alaska....this time she just blew past the ground agent who was trying to get her to gate check her bag and told her "you can't make up your own rules, sorry"
and she stood her ground until the ground agent gave up...
that's delta....but those issues happen on their domestic flights...
i haven't had that sort of thing happen on their international flights....yet..
the most exciting thing that happens on delta international flights (other than underwear bombers) is at detroit airport, you often have to run a gauntlet of treasury officials - they dress in black uniforms and look like gestapo....but they're looking for very specific people, so other than being very nasty and looking threatening, you have nothing to worry about.
actually, i don't know if they're ever at the gate of the heathrow flights - they like to harass the amsterdam flights....i guess there must be people on those flights trying to smuggle out large sums of cash...