Fozzie is half Cardigan... and, I definitely plan on getting a blue merle Cardigan, next.
I have 2 Cardis on my Flyball team, and I've met several Cardis. All of them are awesome dogs! All have been very friendly, clownish, and all of the dogs I've met have had a good amount of drive. They do *seem* less bouncy than Pemmies, and less vocal, but that could be due to many variables... Pemmies are obviously MUCH more popular, and there tends to be way more bad breeders of Pembrokes. I think the lack of Cardis in performance events is mostly because there is simply a lack of Cardis, period.
The biggest dilemma I've noticed with finding a good Cardigan breeder, is the total lack of them. I was set up to buy a blue girl from Pawcific, right before I adopted Fozzie... and they are in Washington. I only know of one reputable breeder in California, and they don't even breed Blues. Many Cardi breeders are divided, in that they only breed Brindles or they only breed Blues (both breed tris and reds). Brindles are not supposed to be bred to Merles. But, if you're willing to travel, or you're lucky enough to have a local breeder, that shouldn't be a problem. I guess I am extraordinarily picky, though, so it's even harder for me!... I will only consider a breeder that shows AND works AND feeds raw. hehe.
I am soooo jealous that you get to go to the national specialty! =D That is a whole lot of Cardi cuteness!