I know that I am very late in on this but we have a 2016 Coachmen Apex 300BHS and we have had it since April. I got 6 trips in for 25 total nights this year. We love it.
We have had some of the same issues but our dealer has been AWESOME and has fixed them all no problem at all (Get-Away RV in Abbotsford BC - they deserved a plug).
No heat in bunk room at first. They fixed it. Apparently that is standard from factory to not have it connected.
Storage compartments would open even when locked - they fixed it.
Oven would not work but they fixed it. It has broken again now but I shut the unit down for the winter so I will get it fixed early April next year.
We bought the anniversary edition package (or whatever they are calling that now) so it came with the brown nose cap, blue led lights, lazer etched glass, higher kitchen faucet etc but like others I changed the few no LEDs to LED.
Really no other issues, we love it. You are correct in saying that the mattress is terrible so I have ordered a sleep number RV size and it will be here soon.
We did buy the 7 year extended warranty. One fridge, one slide or one any big issue will make it worth while.
Good luck with your unit, I hope you continue to enjoy it.