I've have/had various Rainier items. They are "designer luxury" grade in my opinion. Sort of like the Chief's marked police vehicle compared to the regular patrol officer's version, the type that have all the bells and whistles, but cost the part as well.
The Rainier products I have used I cannot complain about, I currently have a MOD3 lower I use all the time and the guys I know who have Rainier uppers are content with them.