You'll just have to decide your poison. Of course if you look on here, you'll see many of the members venting, but this is a nursing forum. We have to vent to people who will "get" it. It doesn't mean there aren't those of us who love our jobs, but on that same note, that doesn't mean there aren't numbers of us wanting to leave. I just passed boards a few weeks ago, but I come from a family of nurses, many of whom gripe about the changes in the field, how the patient population has changed (patients who drink too much, patients who ate too much, patients who had too much tylenol, patients who smoked too much, etc), and how the new nurses need to learn and not just repeat what they've seen in the book (they gave me that speech too).
I see why you like the ICU -- I think that was my favorite clinical, but I think you might want to check some of your idealism, not all. If by "idealistic" you want to make someone smile, brighten their day, etc., you probably will, but you'll probably also remember the one patient who just had to have his morphine while you were in the next room running a code or the family member who could've sworn it was YOUR fault their loved one was crashing when it was probably the previous shift's responsibility that stuff went down.
There are some units where I can see it being more cutthroat than others, but that really depends on where you are. You can find that in any hospital across the country, or really, across the world. I will say that I've seen more units be more supportive of each other than units that are toxic, but the toxic ones (so I've seen) really stand out. That's also heavily dependent on the person in question and the personalities you come across.
I hope you make the decision that's right for you. Doctors have their own way of dealing with people, but I found while some nurses are catty, some doctors are just snooty or *******. Then there are the awesome ones