I was on slingshots pro FS/FS plan and was getting up to 16 megabits! But now That I have swapped to the FS/128K plan I can only get 4-5Megabits is this normal? If it is I might as well pay the extra $10 to get that extra speed. :D
The normal downstream traffic is for downloading, which requires ACK packets and other control data sent upstream. If you can only send at 128kbps then the download will come back at around 4Mbps. It probably doesnt make any difference for viewing website etc, but if the 128k upstream gets congested then you wont be able to do any voice-chat or gaming at the same time.