As another user said, they are now throttling after 2.5 GB of data use -- and that is 2.5 GB total data, not just the data downloaded over WiMax. This is also true for users with LTE phones, they are also throttled after 2.5 GB of total data usage.
I agree with SuperAfnan about WiMax, even in the cities that have it, coverage tends to be very spotty. If you live in an LTE city, LTE would be the better purchase. Though I also find the GSM carriers/MVNOs to have much better speeds, overall, than Virgin and the other Sprint MVNOs.