A friend of mine was staying with AT&T because they had the grandfathered in 'unlimited' plan but when they figured out it really was a 2GB plan and a throttle that let them change carriers without feeling like they were "losing" something.
This is exactly where I'm at now. Been evaluating leaving our unlimited data plan because it seems it's effectively a 3gig plan that doesn't allow tethering. For the same cost I think I can get 6G shared with my wife and tether if I need to.
