I remember being an MS3 and reading SDN. And I remember getting really angry at the people who would condescendingly say, "Oh, you probably never had a REAL JOB so that's why you don't like xyz about MS3. I guarantee that I will LOVE IT in 2 years."
And then in 2 years, they'd be posting on SDN, "OMG I HATE THIRD YEAR CAN IT BE OVER ALREADY???"
MS3 is not like any job.
At a real job, you are able to request a day off to go to the dentist or be at a friend's wedding. As an MS3, it is a crapshoot. One of my friends asked, a month in advance, if he could take a day off to be in a friend's wedding; he was yelled at, told he wasn't taking the rotation seriously, and that he would have to come in an extra weekend to make it up.
At a real job, you get paid, As an MS3, you pay for the "opportunity" to be there.
At a real job, the job requirements/expectations are clearly laid out. As an MS3, attendings and residents will spout phrases like, "read more!" or "be pro-active!" without any clear idea of what those things ACTUALLY ENTAIL.
At a real job, you'd never put up with physical abuse. As a med student, I guarantee that, at some point, a nurse, a scrub tech, or a unit secretary will smack your hand, push you aside, or otherwise touch you in some unpleasant way. And you'll be expected to take it. Because everyone else is "more important" and "more valuable" than you.
At a real job, if you're "in the way," you're told to leave. As an MS3, if you're in the way you're told to leave....and then yelled at for not being "interested enough" to stick around.
At a real job, they have some interest, and take some effort, to give you the basics to make sure that you can do your job. As an MS3, you have to completely fend for yourself. Your resident may promise that they will "page you" when you're needed. And then when you don't show up, they'll later yell at you because "WHERE WERE YOU," even though you weren't paged. As an MS3, we were not given access to the X-ray system (PACS) because it was a "HIPAA violation." And our badges were not activated to allow us into the OR or the ER, so you'd frequently have to beg someone to let you in.
My favorite was when I showed up at the hospital early, like 4AM, to see all my patients before rounds. But, of course, nobody ever decided to mention to the med student that her patient was going to be going to the OR and then the ICU, so it was kind of a shock to walk in to her room and see a completely new patient.
At a real job, your time off is your own. When you're an MS3, even if you do go home at a reasonable hour, there are always presentations, journal articles, and exams to prepare for. Your time off is NEVER your own.
And this is coming from somebody who actually LIKED 3rd year. So please, don't lecture people about it when you haven't done it. I know you may have had a bad job or a rough job in the past before med school, but MS3 isn't like any other job out there.