I used them to buy my 15-85EFs from Adorama. I scheduled six equal payments through on-line banking and had no problems. I am not sure, but I think they also require minimum monthly payments. But if you pay only the minimum, you will not have it paid off within the six months.
The one "gotcha" is that, if you miss a payment or don't pay in full within the six months, they add retroactive interest, possibly as high as %30.
Other stores, such as Best Buy, often have similar deals, with the same requirements and the same "gotchas".