I have one, a border collie/ australian shepard mix. she is a great dog and smart as a whip until her instinct take over and then she can't make herself listen.
She has like 30 toys and knows what each one is and can pick it out from the pile by name.
However, we have never used her for herding, so she is not trained in that area, so she needs fine tuned. She is 10 now and absolutely the BEST dog we have ever owned.
She does bark and go mad when the phone rings, and every time we get out of the bathroom after a shower, she HAS to chase the cat. I do not know why.