Jobert as you read my answers keep in mind I'm a total newbie.
We really like the 391 layout. There is storage under the bed but two extra folding dinette chairs take up some of the space. There are four drawers, relatively sizable, in the bedroom and one of the four closets is plumbed for a washer/dryer. Like all the UFO's the 391 has great basement storage with the center a complete pass through. I like to talk to the wife easily when we're driving and the gas pusher makes that nice. I know she complains about engine noise in the back when she sneaks off for a nap when I can't take the helpful driving hints anymore.
Our use is primarily around dog events. We have three Portuguese Water Dogs and trial them in agility, water trials and have one shown in conformation occasionally. Three 60 pounds dogs going in and out puts some wear on the ol' bus but the G'town is holding up. I can't speculate on full timing but comparing against other rigs I've been in at dog shows it looks as good or better than most. We took the dinette out and have three dog cages in its place. I'm going to build a table top to match the interior wood and we can quit eating off trays.
Problems so far have been hydraulic pump failure during my owner's demo. Couldn't raise the levelers or bring in two of the slide outs. Dealer repaired. J-trap below shower cracked probably during manufacturing assembly. Another 391 owner had the same problem. Hope they fired the assembler. The weld on the door stop broke during a high wind at opening. So far the reweld is holding. I do experience the rebound porpoising I've read about in forums here and will switch to the Koni FSR shocks when I get a chance. I hear a clank noise when I make sharp turns at slow speeds and need to get under the coach and look for trouble. I'm not sure how to check the fan clutch assembly but printed out all the serial number etc. data from a post on this site and will try to look into that. I have watched engine temperature taking the Grapevine in S. Cal and no impact that I could see. I also got 8.1 mpg on a 1,000 mile trip doing no more than 60 mph so I think my FCA is ok. I'm out of UFO warranty in April so time flies. Given what I've heard about RV problems and thinking about a small earthquake rattling my house repeatedly as I motor down the road, I think the 391 has been highly reliable. I just ordered a new water heater anode cause mine is all but gone in less than three years. I think that may be due to lack of use when it was on dealer lots and never drained or properly maintained. Oh yeah, I have a small plastic retainer on the partition sliding door that failed so I have to get another from the factory. Meanwhile a straightened paperclip wrapper around the hardware will do the job and will be unseen. That's it as far as I can remember stuff. I've made many of the newbie mistakes but learning is fun and forums like this one are wonderful for an education.
Hope I answered all your questions and will be happy to get more specific on any others you might have. For the money I believe the UFO chassis and the G'town 391 are a bargain. I paid $87,000 plus California taxes on our 2007 unit with NO wear and tear and 6,300 demo only miles on it last October. I believe I got a great deal. I'm sure somebody's cousin in Des Moines could have gotten me a better deal but don't tell me about it. We've been on hiatus while my wife went through chemo and some foot surgery too. We are soon going to be back on the road and can't wait.
Keep the shiny side up.
George