The guidehorse foundation has been around for almost a decade which is hardly experimental
I know they say they are still experimental but I think they're just being humble.
Based on the estimates that only about 10,000 people sue a guide dog I would imagine less than a thousand would even be interested in a guide horse, let alone be suitable to have one. I know the first guide horse is actually in my state and has had wonderful success in returning a normal life to his handler. He goes on planes, etc and is absolutely adorable in person. I just don't think they've completed training as many as they'd like as picking the perfect mini can't be easy. Guide dogs are bred from carefully selected stock and has been perfected over the years. I'm sure in another 20+ years they may be well on their way to similar.