I want to like OPR so much but it's just too samey - every faction has access to all of the special abilities like FNP or Psykers. And their addiction to only using values of 1 or 3 on wounds/damage, and only values of 1 or 4 on AP is too arbitrarily limiting. Even multi-damage wounds/shots are always factors of three.
They should at least have some variability in the unit stats. That would still be just as straightforward and avoid all the weird rules interactions and gotcha moments - but would be far more interesting, flavorful, and make factions unique.