The problem is that it's quite literally not fit for use. It's some completely fucked software rate limiting or something that produces insane packet loss, pages don't load at all, IRC barely works, ssh breaks up and dies.

I don't mind being shaped to 5KB/s, but at least give me something resembling a consistent 5KB/s, not 12KB/s for two seconds and then 300 bytes/s (actual measurement) for the next half hour at 50% loss. It is quite literally unusable, even if unlimited. And I like Tmobile, but they don't even let me buy additional data.