In the month of May, I actually used roughly 50GB. It was the first time I broke 10GB willingly. Previously, I'd let TitaniumBackup run on 4G just for fun so I could justify the high price I pay.
House flooded and my temp house didn't have the internets, so we abused my tethering. It.felt.great!!!!!
Regardless, I guess I'd need to know how the slow down would work for me to be outraged. If it means it'll slow down to a max of let's say 5mbs.....I wouldn't shed a tear. That's still fast enough to stream in HD and while your download/upload rates might suffer, hypothetically you're still doing better than many folks who pay for DSL!
If it got slowed to like 2mb....I might wanna throw a fit.
Regardless, as long as it was still unlimited, I wouldn't be mad. I know though that now I gotta get my brother a new phone before OCT, as he still has an iPhone 4 that's on 3G. Time to plan the unlimited plan shuffle on the family line....