Not to pour cold water, but download accelerators have quite a fair pinch of snakeoil about them.
At least for HTTP, multiple connections really adds robustness and not speed to downloading, yet they've been hyped for ages.
EDIT: it seems to be a peer-to-peer as it claims using networked computers, or maybe it's server-peer based - that will speed you up but the details are very unclear on their site, which I find worrying.