Sure, pilots are paid to use their judgment. But what pilot wants to say "No" to a mission in which he could save a life ... even if the weather is marginal, at night, and near the end of his duty day? I'm curious as to how much "judgment" an EMS Op Specs allows a pilot to use, without fear of losing his job?
Count me in please. Just because the weather might still just barely be legal to fly tonight doesn't mean I should. Every mission is different and that must be taken into account. So yes if it's marginal enough that I can't do a trip then so be it, dispatch better have a Plan B cooking. When we turn down a call due to weather we copy and paste the appropriate TAFs and METARs into a log so it's plain as day that we simply couldn't do it.
I don't mind leaving for a call if my duty day is nearing it's end though. If there's time to get a patient to a hospital that's fine. We just inform dispatch that if we turn into pumpkins on the hospital roof, the machine isn't moving until our relief arrives. Wouldn't be the first time I've left a helicopter on a pad and gone back to the hangar in a taxi. It's a pain in the butt, but the mission was completed and no one violated duty limits.
It may sound callous, but I'm with Gomer too when it comes to allowing the patient to enter into the equation. I don't let their welfare go past idle curiosity in my mind, otherwise my brain is in the wrong part of the helicopter.