I ate a grass carp once after catching it on a fly rod I had originally rigged for bream fishing.
There were a lot of them in this small lake, and they'd hit the surface like crazy after someone mowed the grass (they'd throw the grass towards the water).
I tied on a green dry fly and tossed it in front of them with the grass. After a few tries, I had one swallow the fly and peel off every inch of my line. I ended up chasing it down the bank, with nothing but the knot around the reel holding the fish on (the 4-lb test leader was pushed to its limits).
I finally got the fish to the bank, and a friend ended up getting in the water with it to pull it up on the bank. It weighed about 7 lbs, which might as well have been 15 on that light tackle - very FUN!
I filleted the carp and my dad put it in a pressure cooker - they have lots of crazy bones in the meat. The bones cooked down, and the meat became soft enough to form into patties. We breaded them and fried them, and I thought they tasted EXACTLY like salmon patties. In other words, they were fine, but nothing to get all worked up about.
All that said, it was so much work that I'll never do it again. It was fun to say that I did it, but #1 - someone paid to stock the fish in there at some point, and #2 - it's not worth the trouble for a fish that you have to do that much prep work for before getting to eat.