First off, howdy and welcome to the forum
I, personally, love quarter horses. Because there is such diversity, you can find one to match pretty much whatever you want to do from cattle work to jumping and dressage and everything in between.
Of course, like any horse breed, there are individuals that run the entire spectrum from amazing and bombproof to snorty and hyper-reactive, but from my experience, many of them are very level headed, smart, and quick to learn. They are athletic and willing and capable, just a great breed for pretty much anything.