I give it about an 8. There are features I would like to see that would add a lot to the horse gameplay.
The horses are great, animations are well done. I would have liked it if you could manipulate their shape more in CAS like you can with human sims. Coat painting is great, you can really make some unique looking horses.
The horse themed jobs on the job board are a nice touch.
Things I would like to see that are not there:
The ability to build and run a complete jumping course. If I am mistaken please let me know but I have only been able to get my horses to do 1 jump over and over. In the sims 3 we could build elaborate courses and run the whole course. I would like to have that ability.
There are no English themed riding clothes. I know it is a western themed pack but they gave us English saddles and show jumping so attire to go with it would be nice.
I would really like to see the ability to Breed your mare to NPC Stallions at the equestrian center and also to offer your stallions for stud at the equestrian center as a way to make money. These seem like things that should be in a horse themed pack. With the household limit still being 8 it would be nice if you could just have a couple of nice mares and pay to breed them just like you would IRL.
Other than those nitpicks I love this pack and had to have it. Horses are the only thing I wanted from the sims 4 and we have been waiting for a long time.