Never used them but you can read reviews here.....

www.transportreviews.com

Keep in mind some are only brokers and your car goes into a pool on a website where drivers can pick and choose cars in route. Some have holding yards where you car can sit for weeks waiting for a full load going your way. Wish I knew about that site before I had my car shipped from CA. My carrier was not very good. And not very "Dependable" to say the least. If the car your shipping is really nice use a enclosed carrier service. It's well worth the extra money. JMO....