The BE provided noise canceling headphones are not nearly as high of quality as the ones you might bring aboard. If you're picky about your audio quality and have a nice pair, I'd still pack them in your carry on.

Just took that JNB_ATL round trip last month in BE - and although, as others said here, meals are "scheduled", the main portion of both flights is sleep time for most people. If you aren't sleeping the entire time, there are snacks available all the time and once the FAs know you are awake, they do a nice job of cruising by periodically to check on you.

I think you have to be pretty picky about the headphones to bring your own - the ones they provide block noise quite well imo.

And the E15 lounge at Hartsfield (if you are leaving from terminal E) did have a good selection of munchies and was a fine place to hang out prior to the flight - I, like you, came from SEA and had several hours of waiting.

Both crews I had did a nice job.

It is a 777, so I believe they only arrive and depart out of Concourse E. They are capable out of T, but from what I have seen, it is not common.