I played OPR for the first time recently too, although I did a smaller 750 point game of AoF just to get a grasp on the core rules of it. Took around 30 minutes to play and was mostly just my friend and I throwing our models at each other instead of doing objectives.
It was definitely enjoyable but I think it's too simple for my taste. Admittedly this is partly due to me doing such a small game without any real objectives. But I'm also just not the type of person this game is made for since most of my favourite wargames are either decently complex or have pretty involved list building, neither of which are the case in OPR imo. I did really like some of its rules though: the morale rules in particular seem really cool as a movement control mechanic and I might try a few more games just to play with it.