David Pogue adores the Novatel MiFi 2200: The tiny cellular gateway, which has a built-in Verizon EVDO Rev. A modem, sports a swappable battery and a tiny form factor. Pogue loves the notion that he can have a Wi-Fi hotspot on demand without any fuss of swapping in cards or hauling a large-format device. He found the device had about 4 hours of battery life in active use, but turning it on and off as needed can stretch it to a day. Standby is rated at 40 hours.
Verizon's pricing is its usual awful level: $15 for 24 hours, $40/mo. for 250 MB per mo (10 cents/MB or $100/GB thereafter), or $60/mo. for 5 GB. Two-year contracts for subscriptions are required, but that discounts the MiFi to $100 with a rebate. A no-contract purchase is $270.
I'll be more excited about the MiFi when it's bundled with WiMax or Verizon, AT&T, and Sprint get more realistic about the data people consume on 3G. Heck, the MiFi could be a multi-mode device and connect and extend Wi-Fi devices to your own private, encrypted Wi-Fi network when available, using 3G only when needed.