We were allowed 3 months off campus. I did an away here in the US and one in Australia.
In my case, the US elective was not to show off, but really just to learn (I was in the PICU) and also hang out with one of my best friends from college/med school who moved to that area for his anesthesia residency. In the end though, I found out a lot about the program and it turned out to be a place that I applied to, interviewed and ranked moderately high (I matched a choice higher up on my list). All for a program that, had I not rotated there, I wouldn't have even applied to. So the benefit can be in going to a place to explore it, but if you completely suck on the rotation it won't ruin your application process (which is always the danger for a true audition rotation).
This is of course specialty dependent though. Pediatrics is certainly very different than say ortho, which places a notoriously high value on audition rotations when it comes to the Match.
My rotation in Australia was much more geared to getting to travel, and see another country. I did learn a lot about the differences in medical education between here and there, but I really wasn't interested in learning too much about adult cardiology...