Hi Nick,
I did EXACTLY what Woody Allen describes (In fact IIRC I think he advised me just over a year ago).
I can confirm that 'over concrete' it is fantastic, it's warm, comfortable to walk on, doesn't damage your tools when you drop them, and worked out cheaper than the other options I was considering. Oh I nearly forgot, you can position your machinery anywhere.
I have put a coat of varnish on, mainly in the 'high traffic areas' to prevent the strands in the boards working loose but this may not be essential 'cos where I've not varnished there is no probs. (That's after one year,)
I did have 2 inch foam slabs laid into the concrete which I would say is well worth doing if you've got the height.