A few improvements I have noticed on my 05 mountaineer that Keystone did that have been discussed on this forum.
First, all of the holes in the floor and the belly pan that have waterlines etc. going through them have been sealed with expandable foam. This must be the arctic package upgrade for the mountaineer
Second, the water pump is mounted on rubber and has flexible lines coming off it. Pretty quiet compared to my old TT.
Thirdly, mine came with the Sealand porcelain toilet standard. A pleasant suprise. Much nicer than the plastic ones.
THese are all things that I have noticed discussed on the forums that owners have had to do themslves. It's nice to think Keystone might be monitoring this forum and taking suggestions!