Your link makes interesting reading - I didn't know Shearwater ribs. One thing I found interesting was the specs. of the boat of the boat put it in the same league as many of the other big players you often read about, but this is carefully descrbed as having an RCD category C rating. Most of the others have a category B. Now we all know that these ratings mean very little practically, but this detailed explanation (they don't just state Cat. C, but also go into some depth as to what Cat C. means and the kind of seas you can use it in) is interesting.
Having said that, some of the reviews talk of trips having been made all around - Wales, and Southern Ireland.
One thing I am not convinced of is what, in the picture, looks like a stepped hull. A concept which, BTW, has been violently slated (being described as showy nonsense) in this month's equivalent of Rib International. They consider it as being dangerous when loading onto trailers, and ridiculous on a rib in heavy seas - comparable to having a spoiler on a Land Rover! Albeit, they accept that the stepped hull has its merits in racing. The article also shows a picture of a stepped hull rib turtled and remaining so.
Having said that, I like the look of the Shearwater.