From my experience (10 returns in J) luckily I never had a substitution to a non flat bed yet
I always have received my choice of meals, the Product and Crew were up to scratch and the Lounge at DOH (luckily) never too busy, but the showers are beyond a joke in regards to no booking system but just a random "queue" , yet the attendant s didn't have a clue, so I just gave up. I much prefer the bleeper system at LHR Galleries.

However, like with any Airline, I am waiting for the downfall and the "shock, horror- I expected more than that" moment.
I was close to that when timings have changed meaning I now would face a 8 hour wait in DOH and the phone agents refused to rebook me on later flight from origin to minimise the wait, but an e Mail to the station manager had that rectified within 1 hour
Let's hope it won't happen soon but you be the first to know on here