I have an 8 yr. Old Quarab gelding. I'd say it probably does vary from horse to horse, but in general they're pretty easy to work with.
My guy can be spooky, but I believe any horse that isn't trained to react properly will do the same, and he's getting much better. They have that laid back Quarter Horse vibe, but with a toned down personality of the Arabian. They've also got the Arab smarts, so they train like a breeze. The best part is their willingness to please. Once they know what to do, they're happy to work. They might be gawky looking, but they're pretty athletic.
My favorite part about them is their quirky personality. It may annoy some, but you really have to learn to laugh at them.