We own the Sandpiper 366FL. Same as Sierra but different color schemes. The only issue I have is no access to the bathroom with slides in. Must move kitchen slide out to get to bathroom. Also, storage is lacking in the basement but there is a lot inside. Don't get the theater seating, go with the standard couches, more comfortable watching TV.
Only warranty work done was a bad hydraulic valve for front slide, left landing leg replaced due to leak, floor in hallway had to be leveled and electric heater element replaced. No issues since last July.
Overall, very pleased with our 366FL and look forward to many years of traveling with it. Good luck with your decision and have fun.