Steve-
Well, I can only respond for the F16'ers I know (in the US) and most of us fall into your first category-
We are still trying to "sort them out" completely up here so I don't feel like any kind of an expert on that subject. I can tell you my impressions and experiences and what I have been told but I think this is clearly the largest area right now for gains in our boats and indeed the entire catamaran community. I have both the 21 sqm and 17 sqm chutes for my boat and which is "faster" I think depends a lot on conditions and I am now thinking that in certain conditions a quite small, flat and high aspect spinnaker may be quite a lot faster. These sails add a whole new dimension to our sailing, just like when the "Wild Thing" was perfected or prebent rigs etc. it takes a while to sort it out, especially in a non-onedesign class where many parameters can be changed- And there has been discussion about long poles, short poles, lifting of the bows by spis (allowing planing), steering issues, what's best for a cat rig vs sloop, etc. I have been mostly occupied this last season with developing a means of hoisting/snuffing- which is necessary (on a cat rig anyway) to comfortably just using these sails-

Kirt