Yea...Multiple connections help a lot, especially when the file is on many mirror sites and each site limits bandwidth.
However, if your ISP limits bandwidth (as many do) then DL accelerator will not help at all. It will use up CPU time and sometimes result in a slower download.
My DSL is capped at 300kbps and with or without DL accelerator, the speed is 300kbps. Hence, DL accelerator helps on very few sites where the server on the other end caps bandwidth to less than 300kbps. ALthough, your situation may be entirely different