I recently started using TomatoUSB on a Cisco/Linksys E1200 router and noticed that I had an extremely slow download speed (around 0.5 Mb/s) and an acceptable upload speed (5.5 Mb/s). After checking QoS settings and the “Bandwidth Limiter” tab, I found a forum post indicating the WMM settings severely affected the speed. Disabling WMM increased the speed to around 1.5 Mb/s.
To disable WMM, go to Advanced > Wireless and look for the WMM field.
This, along with a call to Comcast, has increased my WiFi speed to around 7 Mb/s (25+ wired).