I've done flagship first several times DFW-LHR. One huge plus is flagship dining in the flagship lounge at DFW. The meals are actually quite good. Table service from a menu with chef prepared meals. I actually look forward to it and they have very good wine and champagne on offer . As the OP mentioned I have always had excellent service in FF . The seat is indeed spacious and I love how adjustable it is. The padding of the seat is also softer which makes for a better sleep. The mattress pad is great. I get an excellent sleep in these seats. They are starting to roll out the new bedding that is replacing Casper. I got a mix of the old and new bedding on my last flight and the new pillow sucks. It's just a cheap firm foam pillow unfortunately. The food is meh but I think the food is meh on AA in general long and short haul in 1st / flagship 1st / business. If the difference is slight in price / you have a SWU to burn or the AAward price is only 10k more it's 100% worth it.