Nunsuch's are sneaky fast on a reach, the underbody is definitely a modern design which catches people of guard at times, but I do have to agree that they don't point as well, it's just a limitation of a cat rig and the overall intent of the design.
volume is generous for it's size.
Figure out where you'll be sailing and in what conditions and then make your decision. I sail the New England
coast and for some reason it seams I'm just about always sailing upwind, it's just life I guess. Don't choose a rig based on your current
capability, choose it on what you feel will fit your needs, you'll master whatever rig you choose in a short period of time. If the cat rig fits you intended use, go for it.
I've looked over a couple Nunsuch's at insurance
auctions, in which case you really dig into the boat before making an offer, I was impressed with the strength and quality of the boats.