I was a little disappointed with the Assoc quality, but I think for the money the cars are pretty good. My FT rc8 was really sloppy and definitely broke quite a bit. I had spend a ton of money upgrading it so it wouldn't fall apart on the track.
People say they want quality, but most aren't willing to pay what it costs. However, I do think people are short sighted when it comes to realizing what the operational costs are of their car.
My Xray 808 costs a lot more than some other brands along with the parts being more expensive, but I spend a lot less replacing sloppy and broken parts. I basically paid upfront and didn't have to spend a lot on constant maintenance. The car hardly ever breaks (I had two breaks in nearly three years of ownership racing every other weekend and both of those occurred after teh car was more than 2 years old).
From what I can tell there is a noticeable difference between the brands and this is how I would rank them from my experience with the cars from a fit & finish standpoint...
Xray > Kyosho > Mugen > Losi > Associated > Hot Bodies