Kris,
I have been sailing my Nacra 6.0 Express since I bought it in 1998. My crew and I are heavy at 440# combined, so the more sail area, the better for us. Anyway, my Express has the same Nacra 6.0 platform, but they have added a square top mainsail, genoa (big jib, in fact the wire across the deck for the standard jib blocks is gone and the jib tracks have been mounted out on the trampoline track behind the daggerboards. The boat is rated with a spinnaker as standard sails. Other than that I don't think there is much to add. The boat (in my opinion) loses a little pointing ability with the big jib, and when it blows, obviously the jib starts back winding the main sooner than say the stock sails. As far as the rating, well it was 60.2 in 2001 and was lowered to 59.7 in 2002. (An Inter 20 is 59.2) The boat is a lot of fun and it handles the weight fairly well. But, last month we picked up an ARC22, so that is what we'll be racing now. I am still keeping the Express.
Hope this helps.
Don Cook