People because of some restrictions of ADSL, it doesnt utilive full net bandwith givven, 20% are in case ur isp call when in need, other types)cable wireless) dont have this reserve, so if ur connetion is not ADSL ths wont give any results(or worse), gain from this is max 15~20% i got mine from 49 kb/s to 53 kb/s(example)
Once again This works Only on ADSL