There's no reason to give up Unlimited Data. Unlimited, by the true definition (if one looks the term in a dictionary *is* without limits.
The fact that AT&T is trying to get people on this plan to pay for tethering in addition is unethical. Period.
If people "buy into" AT&T's definition of Unlimited = data to a point that we as a company deem appropriate for our profit margin, then... we might as well start redefining many other terms in the dictionary to suit our own personal views.