A rather shorter answer, based on experience in the F18 class: The only people who got stung here were Dart Hawk owners. Although F18 legal, the Hawk pre-dates widespread adoption of the F18 rules (and possibly the rules themselves?) and as such, didn't make full use of the formula. Owners now face unpleasantly low re-sale value as buyers want something that fully exploits the F18 spec. As far as I'm aware, all boats that were actually designed for F18 have retained very reasonable re-sale values.

The manufacturers keep coming up with new toys to have on the boat (snuffers, new mainsail shapes, self-tackers), but the events regularly demonstrate Wouter's point - you can do very respectably on old kit, it's all down to how you sail it.

Paul