We have been full-time in a Solitude since February of last year. Prior to that, we were full-time in a Grand Design Reflection fifth wheel for 4-1/2 years. We like the brand and they have lived up to their reputation for customer service on more than one occasion. That said, the build is not that much different that any other mid-price-point towable RV. They all use the same appliances and components made by a few manufacturers (refrigerators, furnaces, ACs, etc.) and the only issues we've had with either of our GD RVs were with those vendor-supplied components. GD quickly stepped up to the plate and remedied the situation.
There is a very good forum of/for Grand Design RV owners where your friend can get a lot of feedback (if he's not already on it). Google "my grand rv."
Rob