My 16GB of data use mostly came from streaming movies and tv shows on VEETLE app. I did use it a lot surfing sites like cf.net. Streamed a lot of music and films mostly.
This T-Mobile gets you with that $50 plan by forcing you to pay more for crappy phones. You people are nuts for using that much data on those little screens BTW. (obligatory get off my lawn .jpg)
the iphone did kill ATT's network. and now people who switched from other networks to get ATT won't leave. hell a lot of people still don't know other carriers offer it now. it's probably going to take ATT years to recover from the overpopulation they got from the iphone. Scionxa is right about the hand off re: cdma and gsm. with ATT (i had sprint for 8 years)...the calls just drop so randomly. there's no "fading". with cdma..you could kinda tell when it was going to get dropped.