iPhone 3GS 3.0.1 bluetooth tethering reaches almost 2Mbps!

Look at the above performance monitoring graph that shows that alsmost 100% of its network bandwidth is consuming. (to be honest I saw it exceeded more than 90%) The max bandwidth is 2Mbps. Toooo narrow? You can't say the Earth is big when we are talking about the whole universe. And now I'm talking about iPhone tethering. Usually, it is limited to 500kbps when using USB tethering. When I measured the speed with iPhone 3.0 (3GS), it's never exceeded 500kbps even though the Bluetooth bandwidth showed 2Mbps max.
I'm not sure whether this is caused by the new Windows 7 RTM version or iPhone 3.0.1 updates (but I think it's not likely 3.0.1 fixes 500kbps limitation) or the latest bluetooth driver I installed recently.
I just happened to have thought I'm gonna measure network speed when I opened the browser and felt the loading a page was a bit faster - it's amazing, isn't it?