I’d probably get one if I could get something other than Edge reception at home.
Do you have WIFI at home? If so, you don't need the cellular data connection at home, nor would you want to use it. I use the cheaper $15 250MB plan and make sure I have access to the faster WIFI connections most places I go and just use the 3G when on the road. If I wind up using more, it just adds another $15. Which is what I would be paying every month anyway. So far, I have not gone over.
If you only use your iPad at home with WIFI, you don't need a plan at all.