I finally moved my cellular provider from O2 to Three, because Three has an unlimited data + tethering plan. So far it's been working really well. I brought in my wireless-only Nexus 7 to BNP Paribas' office today, tethered it to my iPhone, and been able to access my email, notes, and other online services quite well. My Nexus 7 is paired with an Apple Wireless Keyboard, and it actually makes a very usable environment.