People who are smart enough can have their Iphones (3G/3GS) tethering in 3 steps without hacking the firmware.
Like I said I have mine through AT&T and pay for unlimited data (30) and my phone plan(40) but not tethering. Most US carriers now make you add data service if you have any type of texting/web enabled phone.
Most nights I get between 1.2/1.3 mb/sec downloads which isnt bad







