It's always nice to save $100, you just have to ask yourself if you plan to use LTE every month. If you are one of those users who use the iPad mostly at home or are in a city with lots of free wifi spots...and rarely use cellular, it might not be.
I am grandfathered into AT&T's unlimited data plan for the first gen iPad. I will transfer it to the iPad mini when I get it. It's worth it for me cause I use the cellular service on the train commute to work every day.
I ditched my cell phone over a year ago and make free VoIP cAlls and texts on my iPad. The mini will be even better as a phone replacement since its not much larger than some of the new smartphones out there. I tested it at the apple store, and the mini fits into my back jeans pocket or coat pocket very easily. Take THAT greedy telecom companies!