I got my Capricorn about 2 yrs ago after having owned a Nacra F18 for the previous two years. Compared to that boat the Cap is, as you would expect, a step forward. It is incredibly smooth to drive, especially upwind. I have found it difficult downwind in heavy airs with a tendency to nosedive. I think this was in part due to a 'bigger head' main that was perhaps to full and was giving too much power and part to me losing confidence. I now have a Landenberger main on the boat and it seems much more controlled offwind. The only build issue I would question is the daggerboards slots which leak at the bottom at the slightest hint of grounding the boards - easy enough to fix (and to avoid!)
For me the Tiger is a bit overlooked now on the basis it is not new rather than its' abilities and is a very good heavy airs boat. The Infusion I would say is a boat that is very easy to go fast on from day one and works well across all wind strengths, with the Capricorn you have to work it at bit more to get the best out of it.
Interestingly enough I believe a Cirrus just won the UK nationals - did someone say the sailor counts for something....