I have successfully tethered my Eris using PDAnet for 2.4mb/s connection. Works great and its fast.
Got speedtest.net score of 1.38mb/s down and .76mb/s up. Pretty decent for my area (NYC)
Please dont post about Verizons terms and conditions. They dont care if you tether as long as you dont go crazy and download like 10gb/month. Yes I used to work for Verizon in the NRB (Network Repair bureau).
Is this riding an available wi-fi signal?
My experience with tethering in the past resulted in 3G speeds between 400 - 800mb/s down (ATT). I think the best I was able to accomplish was a tick over 800 but that was rare. It was usually in the 600 - 700 range.
I'm considering replacing my high speed DSL with a tethered connection and a figure close to what you mention would probably tip the scales in favor. Tethering wasn't horrible at ~700 but I've gotten used to DSL <g>.