It should be noted that the limited data plans for both AT&T and Verizon mean that at the max 4G speed of 73 Mbps, you could use all your bandwidth for the entire month in less than three and a half minutes (2 GB plan). The overages of $10/GB per month on both services mean once you go over your plan, you'll be looking at a little over $5/minute in new charges. It is possible (though highly unlikely) to rack up over…
I bought an iPad 2 last year and I didn't even consider buying one with a data plan. I am near wifi about 99% of the time, discounting driving, hiking, and airplane time. In a pinch, I can check email on my Droid.
Eventually 4G will become inexpensive, but it isn't right now.