The MiFi 2200 requires a special charging cable. The bundled charger works, but normal folks (like me) might assume that any Micro-USB cable will work. They would be wrong.
MiFi
Get a Cradlepoint PHS300 Portable 3G WiFi Router For Just $99!
I love my Cradlepoint PHS300 router. It’s been a constant companion for me for two years, providing Internet access for me and my friends at just about every conference I attend (and organize!) It’s a battery-powered box with a USB port and WiFi radio. Attach almost any 3G or 4G modem or smartphone (other than the iPhone) and you’re online and sharing. And it’s better than a MiFi: You can customize the experience, it’s faster (in my testing), and it scales to support way more users.