I don’t see anything wrong with this. People can read the information and take personal responsibility for their choices.
Menu labeling is only half of the issue at hand here. I think that the notion of The Government using it's sledgehammer to forcibly legislate the entire restaurant industry to comply with specific food and preparation choices has gotten a lot of people's backs up. Although I have no doubt that a reduction in transfat consumption would be beneficial for many people (as is the case for innumerable food additives), legislating that NOBODY is EVER allowed to sell such products in King County I think strikes many as heavyhanded when a more gentle education program might be even more effective, and less emblematic of an overreaching Government as well.
Just because Government CAN use it's full might on an issue doesn't necessarily mean that it 'should'.