I always thought that the Hobie-14 was the ultimate boat to learn cat-sailing on, for the same reasons that Bill said a Sunfish was good. Balance, weight distribution, tacking techniques, etc. - you get fairly instant feedback when you do it wrong and when you do it right. It's true that this boat may amplify some cat traits. For instance, my 6.0 tacks much better than my 14, but it will still go into irons or be difficult if you don't pay attention - but you have to goof much more to make it happen if it does at all. Having learned the technique for tacking the 14 has made me appreciative for techniques of tacking any cat. Same goes for weight, and avoiding capsizes and pitchpoles.
So, in a nutshell, learn to sail a 14 well and you've got a great basis for sailing other cats IMO. Of course, notice that I said learn cat-sailing on. It might not be the best to learn sailing itself on - but with adequate instruction, why not?
I've also felt that the 14 could be catamaran racing's Laser, and that Hobie goofed by not finding a way to keep that model/class alive.