The cell option is a good one for many people, but you do need to be aware that the "unlimited" plans with Sprint/Alltel/Verizon/AT&T are not unlimited. You get a 5GB limit on the high end plan, and less on the cheaper ones. Every now and then I hear about someone receiving a bill for hundreds or thousands of dollars for going over.

Also if you want to share it at home, there are routers that you can put the card into and then it is re-distributed by Wi-fi. We use the Kyocera on our boat and it works extremely well, cost about $150.