Finally got PowerCLI (5.5.0) installed and configured - the scripts above work very well (thanks, again)!
Another question:
I'm reading the docs and think I understand everything above, except one thing - is there a list of all counter groups, names and rollup types of all of the counters available in a particular release anywhere?
(Googling around shows some posts, however, I'd strongly prefer documentation from VMware proper)