Just bought a 4G MIFI to use with my iPad2 this thing is fast!
I am with Verizon, 5 gigs for $50.00. It is expensive but worth it for me and my business. Since there will not be a 4G Apple anything for at least a year, this is the next best option. Plus I use it with my laptop and other iPad and Playbook. Verizon has a special going on today and you get the 4G MIFI for $100.00.
How is the battery life?
Sprint OverDrive Pro Review
If you get good Sprint / WiMax coverage in your area, this is the way to go. Only $45 a month with unlimited 4G /3GB 3G
I don't think Sprint will head in that direction, at least not for awhile. Even if they do, usually they grandfather plans. This thing is awesome, much better than using the crappy ass free WiFi in Starbucks