iPhone Slow Internet Tethering Fix
I had just started tethering my netbook to my iPhone 4 on Telstra but found it to be pretty slow and sporadic. My Skype connections would cut off and my streaming videos seemed to stutter.
I found that the fix for me was to turn off push notifications. That seemed to make the connection much smoother and fixed the Skype video dropping problem. That's my experience but worth a try if you have similar problems.