I found Summerhouse food to be fine on my visit - it wasn't spectacular or the best meal on property, but there was nothing bad about it. Being an American, slightly leaning towards healthy/fresh fare, I expected it to be light on the seasonings which it was - at places like that I always request salt and pepper at the table to put a little pop back into somewhat bland dishes - but everything was cooked properly and of good quality, so with a little pop of S&P, it was fine for me. One reason I like ethnic food restaurants, and 'southern cooking' restaurants, is that they're not afraid to use lots of spices, oils, butters, fats, and other things that make the food tasty and interesting. I still enjoy the high quality meats and vegetables at some places known for 'healthier' fare, but find I need to add my own basic spices sometimes to wake the food up a bit. I'll request extra butter, salt and pepper and add as needed to meats and veggies at those places - and again, I'm not disappointed when the food comes out a bit more bland because I knew that going in.
There are some places in Disney where I haven't really liked the food much, and others that I find reliably good. I don't expect the finest restaurants I've ever seen at amazingly low prices when I'm at Disney - I expect everything to be overpriced, but with the wide selection, can always find some good spots to eat when I'm there, and sometimes even specific dishes where the restaurant may not do other things well, but can do that one dish well. And yes, they change around enough that sometimes a once-good restaurant goes downhill, and occasionally a previously poor restaurant improves with a new chef or menu. I'm at Disney 20-30 days a year and probably less than 5 of my meals each year end up disappointing, 15 - 20 of them end up being satisfying, and a handful end up being very very good.