I have had great customer service from both Country Supply (which is horse.com) and Valley Vet.
I think I am switching most of my ordering to Valley Vet though, because they have better tack. I love Country Supply and they are great for dewormers and fly products, but it seems like lately they are getting out of their better tack and adding more junk tack (especially when you look at their saddle line lately).
Valley Vet has similar prices on dewormer, maybe just a dime or two higher, but if I plan to order a tack item along with my dewormers and fly control, I will definitely choose Vally Vet! Plus, Valley Vet often has free shipping and Country Supply charges shipping now.
By the way, I placed my first order from Valley Vet last fall because they had Classic Equine Alpaca cinches and Country Supply did not. So I ordered one and I LOVE, LOVE, LOVE that cinch!
It is super soft and doesn't have the "stretch" that all of my other mohair cinches have. I usually have to buy a smaller size to factor in the 2 or so inches of stretch but this cinch didn't really seem to stretch. I don't know if that is the Alpaca fiber, or because Classic Equine makes a better cinch. Either way, if I ever need to order another cinch, I am getting another Classic Equine Alpaca.
It also seems to stay cleaner than my mohair cinches. You know how after a while when the horses sweat your cinch gets really dirty and kind of gummy? Well, I know it is winter and all, but this cinch seems to stay a lot cleaner than my mohairs so far. I wash my cinches whenever they get dirty, and I haven't had to wash the Alpaca cinch yet.
I just thought I would mention a positive plug on the Alpaca cinch because I had trouble finding any reviews of the Alpaca fiber cinches vs. regular mohair. I'm sure the Classic Equine Mohair is nice too, I really like their products!