Agree wholeheartedly. The best design teams are ones who either “know how the sausage is made” (that is, have a general knowledge of how their design would translate to code) or have guidance from developers on what is and isn’t feasible. The really good ones know the quirks of the platform and will design around them (for example, messing with UINavigationController on iOS breaks a bunch of things and is generally not a good idea).