First off, this posting is not meant to offend contractors. In my thirteen years as a designer I have met a number of contractors that I respect and who are genuinly trying to do their best. This is my take on the relationship between designers and contractors on a jobsite.
A designer's role within a project is to represent the client on the job site and to make sure that the project that is finished represents the project that was designed and approved up-front. That means that we are hired to be the bad guy and to nitpick and to point out any variations from the design plan or slight inadequacies. All of this is done in the hopes that the finished product will be taken to a higher aesthetic and quality level. In my mind this relationship is MEANT to be tenuous at times with each party working toward their absolute best interests.
So, is it really possible to find successful "teams" of contractors and designers? Does this mean that a designer can't work repeatedly with the same company? No, but in my opinion it does make it hard to find a company that you want to align with, because that means staking your professional reputation on the work of another organization. If a designer does get into a "partnership" with another company the challenge would be to maintain objectivity.
This is why I choose foe. Because looking from the eyes of a client- I want the creme de la creme and if you want to keep us happy then you need to bring your A game!