As a former surgical PA and current General Surgery resident, I have done BOTH jobs you are discussing here. From my experiences, I can tell you that those of you who honestly are worried about PAs taking your job should find something more useful to worry about, like a meteor hitting Earth or being attacked by Bigfoot.
As someone previously mentioned, the overwhelming majority of surgeons (as we have all experienced in countless conferences and interactions) recognize that even the most "minor" operations can have major complications. BY LAW, a PA MUST have a supervising physician in the area they work in--they can not obtain a license or hospital privileges without one. Even those who are employed by hospitals MUST have a supervising physician. This means that any and every PA you have ever seen in the ORs have a SURGEON on their license and hospital credentials. If that PA EVER does anything wrong, that surgeon is liable for any complications. Very, very, very few surgeons (if any) are ever going to put their name or license on the line so much as to allow their PA to operate independently skin-to-skin, even those they have known for years and have trained. These surgeons know that years of "apprenticeship" or even a one year PA surgical residency is no substitute for a medical degree and 5+ years of residency and/or fellowship.
I was treated well as a PA, and I am treated well as a resident, but I am treated different. My job as a surgical PA was never to train me to become a surgeon, it was to take good, comprehensive care of the surgical patient. Most of that care was outside the OR but some of it was in the OR. So what?? When you get to be a PGY-5, let me know if you really think you needed a few dozen more skin closures to feel competent. And if you WANT to do more vein harvests, then ask the PA to teach you and let you do them when you are on your cardiac rotation. I assure you most of them would be happy to help you. As far as billing, yes, PA's can bill. That is why the attending would sometimes grab me to round with him or her--when short on time we can run through the patients quickly, I can fill out the billing forms as we go and the department makes money. Teaching is imperative for certain, but any department that isn't wise about billing is NOT a place where any of you want to train--trust me.
The grass is ALWAYS greener on the other side, and as residents I can understand how looking at the midlevels may make you envious, resentful or even worried. But I can assure you as someone who knows many, many, many midlevels and used to BE a surgical PA, they will NEVER take (and by and large don't want) your job as a surgeon. Those few that do will realize that there is a very defined (even if not evident to the residents) ceiling of knowledge, skill and scope as a midlevel and like myself spend a lot of time and money to go back to medical school and do a surgical residency.
I am not an unintelligent person--there is no way I would have gone through medical school and residency if I could have done what I really wanted to do (be the surgeon) as a PA!