I think developers must understand that designers know their stuff and should let them just do their thing. For every 10% of value that you think you are adding (-- hey, I think we'll just use Arial instead of Helvetica) you reduce their commitment by, like, 80%. (Complete paraphrase of something I read on a book I can't remember)

When I had the chance to work in the cakePHP website they were 100% hands off and just let me run wild and do my thing. That has not happened again in my career and I think that continues to be the major highlight in my portfolio (apart from the exciting stuff I'm doing nowadays :P)