That looks like a nice unit. How thick is the steel that they use? In the RF offset that I built, I did not worry about stainless steel grates. I used regular, mild steel for mine and seasoned them well. In 2 years, they have not rusted at all. I like the idea of the insulated firebox a lot. I have heard that the adjustable baffle is nice on a standard offset cooker. As for the grill, that is a personal preference. I like to use a dedicated grill, so it would not be useful for me.
A nation of sheep will soon have a government of wolves - Edward R. Murrow