There's a fair use, but if you go over it, there are no run on charges at all. Only download restrictions from 4pm til midnight until the end of the 30 days.
Browsing is completely unlimited.
But on Pay as you go, that's really the best you're gunna get.
It's only contract which has higher fair use/completely unlimited.
Bottom line is - T-mobile don't have run on charges at all.
Wow, how slow can a connection actually get? They're already damn slow!
Also, there are plenty of PAYG providers with proper unlimited internet. (Well, two, but how many do you need?!)