I don't know of any LWers who have used PB enough to really have a solid level of normal. My own PB stats are badly distorted by all my janitorial work.

I suspect not many LWers have put in the work for calibration; at least, I see very few scores posted at http://lesswrong.com/lw/1f8/test_your_calibration/

So, I couldn't say. It would be nice if we were all calibrated. (But incidentally you can be perfectly calibrated and not have 5/10 of 50% items happen; it could just be a bad week for you.)