OPR (specifically CCWM) is better than I expected at separating teams, and seems to be ~85% accurate based on a comparison to a few events of data.
That said, you have to remember that OPR is an approximation of skill that is better than average score but no replacement for a real scouting system. It's a decent "sanity check" to see if you missed an outlier or two but if you have actual data I wouldn't even touch it.
During and after the season, it's a very good approximation of skill that is very useful for Internet debates.
