There is a farm local to me that used him & Art Deco heavily on their broodmare stock years ago.
My impressions of both were they made quiet horses, but prettier in color than in movement. I tended to like the Art Deco horses in type/movement more, but my roots are in eventing.
The mare seemed to really matter with Sempatico in terms of movement and body type. I saw many I would describe as heavy and coarse.
They have grandchildren of both now still in the program, it looks like their goal is an all around LL mount for average/amateur riders. They do not breed for approval in registries, so take that how you may.