When I flew with Delta last year I thought they were pretty decent bunch.
When I checked in at Gatwick I asked if I could possibly be allocated a window seat. The checkin agent was very apologetic in saying the window seats had all been booked but gave me the best alternative... a seat right at the front of coach with enough leg room to stretch my legs fully straight...
He also allocated my seat for the Atlanta to Miami connecting flight which happened to be the emergency exit seat with the seat in front removed... fantastic, a window seat and lots of leg room.
But not only that he had also booked my return flights MIA-ATL and ATL-LGW so that I had the window seats at the front of Coach with lots of legroom as well.
The flights themselves were all on time, the arrival into Atlanta was thirty minutes early despite a couple of holds at FL280 or whatever we were at inbound to ATL.
The inflight entertainment was pretty standard, music channels okay. They have a moving map system and inflight data system. Food was good with free beverages, but alcoholic beverages were extra. I don't drink before flying or during flight so that wasn't a problem for me.
Be warned about the immigration at Atlanta. We seemed to be the first European inbound for the day (or for several hours at least) so it was our flight at the front of the queue. But it still took me two and a half hours to pass through immigration. Probably because I had an M-1 visa for flight training they put me through "special processing" room (which also acts as a deportation room!).
By the time I got through, found my bag, re-submitted it to the connecting flights checkin... ran to the transit train from concourse E to Concourse A and then rang the entire pier to A2, I had 5 mintues to spare.... If my flight had been on time and not half an hour early then I probably would have missed it thus being put on the next available flight to Miami.
Delta seem pretty good... oh LGW to ATL and ATL to LGW were on Boeing 777's and ATL to MIA (and return) was on a Boeing 767-300. 777's had personal seat back videos (or arm rest videos) the 767-300 had a generic display for the cabin... but the ATL to MIA only took an hour and half and I was looking out of the window at the CB's towering above our FL330 (or whatever) thinking oh my god, I'm going to be doing my IR with these things around???
Best wishes,
Charlie Zulu.