I have that exact RV. We bought our 2018 Chateau 31E new almost 5 years ago, and have used it a lot.
Overall, the floor plan is great for a bunkhouse class C. However, a couple of years ago Jayco came out with a very similar floor plan, except the entry door is moved forward, in front of the sofa instead of behind it. This allows the passenger seat to swivel so it can be used while camping. It would be nice to have that extra seating.
The big full-wall slideout can be problematic. I've replaced the slidout motors once and have had it aligned/adjusted a few times.
As stated above, the rear is very heavy. I had a couple of rear tire blowouts, and replaced all the rear tires with ones that have a higher load rating. I also installed rear Timbren helper springs. Other handling improvements I've done are big swaybars (Hellwig), a custom alignment, a steering controller (Saf-T-Plus), and Bilstein HD shocks.
Another upgrade that also made it nicer was additional sound isolation in the cab.
The engine and transmission seem to be pretty bulletproof, but I did have a cat converter replaced under warranty a few years ago, and I had to replace an O2 sensor last year.