xnr:
It may come as a bit of a surprise, but there are a lot of helicopters out there flying that are Category A certified. The S-76A is one of them, because, unless I'm really wrong, the UK CAA certified it, albeit with a performance penalty.
I'm also pretty sure that the helipads in Canada had a 'let' for something like 'demonstrated engine out performance' - at least that's what I tried to get put in, as we had an interesting situation with the S-76A doing vertical takeoff profiles that were not permitted by the basic flight manua.
NickLappos, I might add, was extremely helpful in getting this situation remedied to the satisfaction of nearly all concerned. Long story.
Category A is not normally required in operations in North America, which is a bit of pity- the requirement does a lot to teach helicopter pilots about performance. This increase in knowledge drives up the safety levels, just by virtue of being there.
One of my friends at a large helicopter manufacturer said there was a different level of operation and safety between the operators of single engine helicopters and twin engine operators, and he couldn't pin it down to anything other than having to consider a lot more when operating the machines.