This review is for the service department only - I haven't bought a vehicle from them, so don't know about the sales department.
I bought a used RV on a Ford E350 chassis last year. The previous owner had the maintenance done at Horizon, so I decided to go there also. I am very pleased with them. I find some of the service advisors a bit brusque, but they have never steered me wrong, and have never tried to sell me something I don't need. When I've gone in there asking if I should have them do some service or another, if it's something I don't really need, or don't need yet, they'll tell me so.
I've also been very pleased with the services that they have done. I feel 100% comfortable taking my RV there, knowing that they are both honest and very competent.
Can't comment on their comparative prices as this is the only place I've taken the RV for chassis/engine servicing. I'm satisfied that they're worth what they charge.