to see how "inverted" or not he got, the easiest way to see is to get a model helicopter and hold it at the same angle as can be seen in the vid.
The point where it gets really difficult for the pilot is when the skids cross over each other while the head is pointed at the ground, try doing that with the model and get the same sight picture, he is well past 90*.
If you really want to see how smooth you are doing turns etc, simply stick a load on your hook, with a weigh gauge. Done badly you could almost double the weight of the load, done well the load on the gauge shouldn't change much at all. I agree that smoothly done turns could have less strain than flying in rough weather, as i have seen hook loads vary by quite a bit while flying through turbulance, however it also comes down to is it necessary, and how much of a cowboy do you need to be.
If that flight is alright, whats everyones opinion of the video of the guy flying his 22 into the landing spot in his hangar? Just because you can, should you? and where is Airmanship in both cases? is one ok because its a 350, the other one not because its a 22? or one is fine because its Europe the other must be insane because its outside of Europe??