Well I have an ACD/rat terrier. I have only had him a few days, and he is 10 months old.
My guy takes after the ACD a lot. He really behaves like a small 20 lb ACD and not much like a rat terrier.
This dog is exceptional. I truly believe you could put him at any task and he'd do well at it. I do agility and dog sports and so he is perfect on that front.
He has more energy than any dog I have EVER had by FAR. His energy level is completely unbelievable. He is very fast moving and is like a little bullet on four legs. I took him to a field yesterday and he sprinted for an hour straight. I mean full out sprinted.
He is very trainable in that he learned sit in all of 1 minute (literally). He learned drop it and leave it in just a few repetitions. He needs no motivation, just doing things is enough. He is very checked in to me already.
He has no impulse control at all. I have small dogs and this is a problem. He wants to chase and bite them.
He bites. A lot. He is very over stimulated by movement and loud noise. Anything that makes him excited makes him bite. Affection- he bites.
He also jumps all over everyone and everything. He thinks it's fun to come full throttle into you and then slam himself into your crotch or at your head.
On walks, he is very over the top about cars, people, other dogs.
He plays ROUGH. He has a lot of power for a dog of his size. He'd fetch till I stopped throwing. He wants everything in his mouth and was dragging my rugs all around just because.
He is pretty much either sacked out asleep or is vibrating with energy. Thank god he has an off switch.
He is in your face and very affectionate (but bitey). He loves people.
He resource guards people and I am sure he would food and toys if I gave the other dogs access to him when toys were out.
I will be honest, I've had a lot of dogs and he's a real challenge. He's inherently a good dog but there is a looooot of energy (I can not overstate his energy level!) and a lot of desire to bite things and people and other animals.