I'm somewhat confused by what this service actually offers. What is the customer paying for? You download stuff, sure, but then they need to download it themselves still. Why wouldn't they just torrent it themselves? What you're offering doesn't negate the overage fees that can be faced by those on ISPs with low download caps, since they have to download it themselves.
Even if their ISP is 'hostile' to torrents and throttles, that may not be any worse than trying to download from direct download sites when the customer is without a premium account.
well, many people I know have ISP's completely block their torrent download capability, anything that looks like a torrent (including blizzard download utility) is completely blocked, thus rendering this service useful.