I am not a huge fan of OS but for the money they are the best running engines out there. Look at rc combat 90% of the engines used are os and they outturn and outlast about anything out there. I have tested many engines (norvel, webra, MDS, magnum) and none come close to the performance of the os.
But those are not the same as the OS .46 AX. That engine is not in the same ball park as a Fox, or Enya. Yes, OS makes a few hot engines, but they have rarely been top of the heap.