Ok, there's enough data now on the other thread to point at least to the fact that by MSS clamping to reduce the TCP datagram size down to 540 bytes gaming can work well down to about 700kbps upstream with highly tuned scripts.
The relevant long thread is Help prioritizing games with alternative qdisc design and you can see graphs such as the ones here to show that ~700kbps ADSL lines can still game like crazy with such customizations even while speed-testing (see the speedtest traffic during the above gaming here)