I'd like to hear about anyone's experience with prepaid MIFI. Here is some info I have:

Virgin Mobile has a new MIFI device, $60 for 5GB

Boost Mobile CDMA and a Windows Mobile phone lets you make your own MIFI for $10 every 3 months. You need to go through some hoops, and this may end when Boost clamps down.

iPad SIM and a GSM MIFI device works if you first activate the SIM on an iPad or iPad simulator. The SIM fits in regular GSM devices if you don't snap it down to the small size. $15 for 250MB or $25 for 2GB.

I currently use the Boost roll-your-own MIFI with a Mogul, but it is a bit flaky, especially if you leave the device on all the time (even if not being used). I activated an iPad SIM, and I like the idea of using it in a GSM MIFI device. A lot cheaper per month than the carrier MIFI solutions.