All pilots have their personal safety standards for weather, and plenty of pilots fly on the airlines when they absolutely have to be somewhere. Granted, that guarantee has become ever more dubious over the past decade, but your chances of arriving on time are still better with an airline ticket.
But most pilots probably look out the window on the way, wistfully wondering whether or not they could have made the trip in their own airplane. While you can't always tell for sure, you can sometimes stop at the cockpit door on the way to the jetway for a chat with the crew to confirm or deny your suspicions. For example, last Sunday I flew in Seat 22A of a Boeing 737-900 from to Orlando for the National Business Aviation Association convention. I had to be here, absolutely, and a Nor'easter was ravaging the Northeast. Still, the weather didn't seem too bad, and I asked the first officer after we landed what altitude we broke out on top after takeoff from EWR. She wasn't sure, but she thought it was about 13,000 feet. A bit high for comfort in my Bonanza. I also asked about the freezing level, and whether she thought there was any ice in the clouds on the way up. She said it was 6 degrees C at the surface, so the freezing level was likely pretty low. She wasn't sure about ice, but her facial expression gave away that she thought this was not a good day to be flying my airplane on this route.
That helped me feel better about not flying myself.