Gwen:
Disclaimer : I'm a student just like you, so take this advice for what it's worth.
Your reaction isn't surprising. Like any other specialty that offers hours and training less grueling than surgery, etc., some students are drawn to PM&R primarily for "lifestyle". However, the key question here is whether you actually LIKE dealing with patients that others may not, or trying to diagnose and treat illnesses that are essentially incurable, or diseases that are relentlessly progressive. The PM&R doc's role is often that of maximizing function in a compromised situation, not curing or fixing. This doesn't sound like big difference from what most other physicians do, but it is a fundamental shift in the treatment paradigm that is difficult to understand until you've participated in it. The same thing applies to both the inpatient and outpatient sides, in my experience. You are often in the position of informing patients that "we can try this or this and you may be marginally better, but you will still have pain and still have functional limitations, albeit lessened." Now don't get me wrong, there are many, many specialized interventions that physiatrists can offer both in the acute, sub-acute, and outpatient settings, it's just a different approach to patient care than what some people expect.
Having said all that, I know how difficult it can be to separate out the experience of a specialty on a rotation from the personalities you encounter during the rotation. Ask yourself what it is you dislike about the rotation; is it the pace, the patients, the physician(s), the staff, some combination of these things? I've certainly been surprised during my rotations with my rather visceral reaction to some of the services I've been on. Some things I thought I might enjoy, I HATED, while some services I assumed I would hate were fun. After two months of PM&R rotations, I discovered that it didn't matter WHO I was working with, I truly enjoyed the field itself.
I realize you have a time crunch at this point; perhaps your best option would be to sit down with a couple of other physiatrists or residents you have access to and discuss your concerns with them honestly. I would be very concerned if I "HATED" any significant part of the field I was choosing. Best of luck to you.