It's possible to have your iPhone only connect to the 3G network rather then fall back to the slower less-data friendly frequencies. Just SSH into Var/Wireless/Library/Preferences and csidata and scroll to the bottom and find 'GsmRegistrationModel::fRatSelection=0x1 and change the 0x1 to 0x2.
I found it useful for areas with weaker 3G[but still very usable] as my phone would fall back to Edge which is equivalent to a 56K modem.
I found it useful for areas with weaker 3G[but still very usable] as my phone would fall back to Edge which is equivalent to a 56K modem.