A close friend who we travel with often has a 2005 34ft Dolphin on the Workhorse frame. He is very pleased with his MH, travels with it often, and has had no significant problems. Sure, the dash air needed service, he had it detailed and the decals removed and replaced with paint, he replaced the front TV with a digital flatscreen, and he has a Banks power pack. I don't see that he gets different mileage from my MH, same engine, longer and heavier, and no Banks, but that is a totally unscientific response.
If maintained, it's a nice RV. Naturally the way an RV is treated has a great deal to do with it's longevity, regardless of the brand.
Happy Trails.