I have to make the same decision- even thought I was PTing in the 160s, I absolutely know my score from yesterday is well below that. I wouldn't even be surprised if it falls in the 140 range seeing as how nervous I was and how bad the proctor/test conditions were.

First off, most schools take your highest score and a cancel or a lower score won't really make a difference, from what I've read. It also may depend on how strong your other factors are. Personally, my GPA is not that great, so I really don't want to explain not only my crappy GPA but a low 1st score as well. I feel like I could explain a cancel much better but eh, who knows. Still got a few days to decide!