Temperament is the same as any other breed. Put the wrong sire/dam together and you have a handful, put the right sire/dam together you will have your dream horse. The sad part is although the chocolate is the desired color that in itself is causing genetic problems in the breed. Read up on ASD, it is not a life threatening problem, but is a defect and as long as breeders are careful and honest I don't see it as a big problem.
The other thing we northerners are adding to the breed is the insulin resistance. These horses are used to eating lower quality hays and grasses and many of us are busily feeding them feeds and great quality hay. Because of this in my area especially many are keeping "fat" horses. I have seen some that no longer gait and end up needing a fat farm.
I have three of the most wonderful horses with great temperaments and before I purchased them I researched the bloodlines for that purpose. Our mare can have a bit of attitude, but still does not refuse what is asked. They are 5, 4 and 3 respectively and are seasoned trail horses at this young age and all enjoy going out on the trail. Plus they have the most fantastic hooves I have ever seen.
A woman can NEVER have too many horses.....