It's worth looking at this thread over on the QR forum if you're thinking of using them. Their seats vary a lot across the fleet. The A380 is apparently very good.
I can vouch for the seats on the 777 as the last time I slept was on one. They're not absolutely level although they are pretty much flat. I didn't have my spirit level with me to prove the former statement.
The lounge at Doha's huge and the showers are good. I didn't hang around long enough to sample the food. There is a quiet area to sleep in if you have a long layover.