It connects to the Sprint 3G/GPRS (in rural areas) networks, and accepts 5 simultaneous wifi connections (b/g, not n). It's about the size of a business card, about 1cm thick, so it's easy to carry. We found the battery life to be around half a day when constantly on. If you're on a long journey you can turn it on/off as required.
It's great because if you have an iPhone/Andriod, you can turn off data roaming, use this, and have maps/GPS and it worked with Skype too. We also connected laptops, in our experience the signal and throughput was good enough in urban areas to watch YouTube/Hulu/abc.com etc in SD and occasionally HD. In low signal areas it was just ok for maps.
Of the hotels we stayed in we had a 50/50 split of free internet or not. When you compare the cost of this, plus a GPS unit for your rental car, and the cost of Wifi at some of the major airports, it pays for itself really really quickly.
Monthly cost for unlimited data is US$50 currently, this may of course change in future. Other smaller options available. You buy the cards at Walmart, Target, 7eleven etc or can top it up with a US credit card. You must buy some credit and a plan at least every 12 months to keep it active!!!
I'd basically recommend buying this if you travel to/from the USA for work or are visiting for an extended holiday.
You get the Mifi, charger, Virgin Mobile account information, pouch. Also currently has unlimited data until the 5th of November.
It works while charging, e.g. you can just leave it plugged in.
Will ship to anywhere in NZ courier post for $10, or pickup from work in Albany.
Please PM me for contact details, or ask a question here, as others may also want to know the answer.