if you want a portable and personal hot spot, you can get Virgin Mobile. It's using SPRINT.
You can also use Freedom Pop. They are also using Sprint.
You can use ClearWire. They too are using Sprint.

All three uses basically the same hardware so if you go to any of the three web site and look at their 4G-WiFi hub or the 4G USB dongle, they look very much alike with the exception of the logo on the hardware. All three have variation on the plans.

MiFi is 3G and you can get it really cheap for either the hub or the dongle. When I need the personal hot spot, I'm roaming so I try to keep my data usage low and below the threshold. 3G is a good bottleneck for this. So I'm not tempted to stream music/video. It's good enough to check e-mail, send and receive messages, even look up information.

Freedom pop wants you to go over the limit so they can charge you big $$ per excess MB of data.
Version Mobile just throttle you by your neck when you reach the limit. I think that is the way with all the other carriers.

Also check Consumer Report 2012 Dec. issue.

Internet connection in US is Byzantine. It's expensive, restrictive and slow... Compare it to S. Korea, France, Japan...