Tire Buyer is owned by American Tire Distributors, which I think is the largest wholesale distributor in the US, but I don't feel like googling for the answer right now.
I haven't ordered from them, but I always check them and sometimes they're competitive on price.
A lot of the tire sale websites are actually owned by wholesale tire distributors.
I bought a set of snow tires from them in 2012. First and only time dealing with them. Shipping was free but I did pay tax. They arrived quickly and had the best price at the time. Would do business with again.
Tires are commodities so make your decision mainly on price. As said above tirebuyer just the customer portal into American Tires.
It ends up being more about the shop you ship them too (unless you're really buying directly to you and you mount your own tires).
Differences in the shop choice will affect your experience more than choosing tirebuyer over tirerack over letting the shop order for you from their favorite distributer (which might be American Tire anyway).
Look out for coupons if you can find one.
I bought from them last year, nothing out of the ordinary, but after the order was submitted, I only interacted with my shop for everything, not tirebuyer.
Last January bought set of RT43 for my Saturn. The price was great with discounts codes on site. Free shipping to Auto Tire that did a great job of mounting and balancing.
Last month 2 Goodyear winter tires from their Ebay store. It was cheaper buying two from Ebay store compared to Website. I took them to Wal-Mart and cost was about $17.00 to mount and balance each tire. Working great.
The snowtires were shipped from New York.