My oh MiFi, Virgin Mobile US mobile broadband for travellers
If you travel back and forth to the US for work, pleasure or long distance yankee doodle, this could be the answer to all your roaming data problems. It's a MiFi hotspot from Virgin Mobile US, and is available in stores and concessions across the country. Similar to the 3 MiFi hotspot in the UK, you can top up the credit and connect up to five WiFi-enabled devices to the device.
There are a couple of potential issues with it. One is coverage; the US is massive, obviously, so check coverage first - Virgin Mobile US is owned by Sprint, who have reasonable data coverage in most major conurbations.
Secondly, the data you buy has an expiry date; $10 (£6.70) buys you 100 MB which must be used with 10 days of purchase; $40 (£27) buys you unlimited data which must be used within one month. That's not too unreasonable, but it would far more useful if the low tariff could be carried over.
The real issue is the price of the MiFi unit; it's $149, so roughly £100 - twice the price of 3's unit. Gah. That's extortionate for a one-off trip, but then if you're staying in hotels for a month, it may still work out cheaper than the hotel WiFi charges.
Of course, if you don't mind hanging around Starbucks all day long like a dickish hipster, then your luck's in - the corporate coffee chain recently announced that in the US it no longer requires customers to log-in with a Starbucks card and offers unlimited WiFi usage, rather than limit usage to two hours.