I just bought a Grand Design Momentum 350G that has a separate 14.5' garage. I thought about ordering the RV from the factory, and would have ordered it without the deck system, because I didn't think I would use it. Our dealer got a Momentum 350G in stock with the exact options I would have ordered one with, but it also had the deck system. I have been looking a long time for this RV, so when he got one in stock I bought it within a week of it arriving at his dealership. After having the chance to use the deck system I must say I really like it. The ramp functions as a deck, with enclosed gates around it, and a rear awning extends the length of the deck to provide shade if you want. I'm glad I have it now.
There are obvious limitations to its use. It will work better in spring and fall when temperatures are more moderate. It will work better if there are fewer bugs. And it will work better on days when there isn't a lot of wind and dust.