Starboard's description of the Rio 2008, which you quote, sounds a lot like my experience on the Kona: "narrower shape and ... daggerboard allows the board to power upwind off the leeward rail. When planning, the tail with large cutaway ... delivers a powerful and exciting ride." The Kona really does have a fast, "adrenaline kick" ride when planing, and is much more manouverable than any other board of that size. Also, the nose rides high and free so you can blast over chop without fear if the wind gets strong.
Of course, if I had the cash I would get one of the new performance race longboards like the Starboard Phantom 380. That would be a sweet machine with a 9.5!