I have a Big Earl inflatable SUP from Northwest River Supplies. I am really loving it! Lots of fun, and getting (learning) my "sea legs" on it is as much fun as all of the advantages.
I kayaked class III-IV whitewater for 9 years. Due to a semi-bum shoulder, I cannot roll one reliably anymore. No, I won't be running the tough stuff on the SUP, but I will eventually work my way up to class II-III stuff. I have machined a "whitewater" skeg for it out of UHMW plastic I had laying around. Very tough and slick plastic that should hold up far better to rocks than the OEM skeg(s). I've also made my skeg more shallow, and will keep shaving down the depth until it just barely works. Without any skeg, it's pretty difficult to paddle in a straight line.
I have also learned that when a skeg hangs up on a rock or tree limb underwater, YOU keep going. Probably pretty comical to watch, but not very fun to do. Been there/done that.
Along with my special skeg, I'm gonna try padding it on my knees, using hand paddles (which will arrive tomorrow). Paddled on knees, it is waaaaaay more stable than if standing up. Plus, with two hand paddles, I have even more thrust and control than with a long canoe type paddle.
I paddled Lake Conasauga with it last weekend. That was a real hoot, and it's amazing what one can see while standing up tall and wearing polarized sunglasses.
I'll also eventually try to fish while on it. That'll be tricky too, as I have found that merely turning my head around to look behind me really throws off my balance.
What I love about an SUP is that it is just about the most "do-it-all boat" there is. Flatwater, mild whitewater, river surfing, ocean surfing, fishing, etc. Not many boats at all can handle that, and be deflated, rolled up and thrown in a back seat, or in a backpack carrying bag. Plus, it is absolutely the easiest boat to carry that I have ever had.
My next SUP will be one that I build. A non-inflatable one will be much faster and easier to paddle. But that one won't be capable of running among rocks. I'll reserve it for lakes, flat rivers, and the ocean.