As a frequent traveller to the UK I recently replaced my 3 USB dongle with one of these. The 3G/3month card is just over £20, and 3's data coverage is pretty good. It works out much cheaper that what the hotels want to charge for internet access.
Generally it was great. The device+micro-usb cable takes up so little room, and the fact that it will charge while in use is a bonus.
Connected iPhone4, iPhone3GS, and laptop to it without any issues.

I only really had problems when it was switching between 3G and 3G+, the internet would disappears for about 20-30 seconds as it switches. If your signal strength is border line it can switch every few minutes. So in the end I moved it away from the window, and it stuck to 3G. Otherwise perfect.

I think your results on both this and the older model may have been contaminated by the proximity of other networks on the same channel. I just bought the car kit (but got the older model - old stock in the 3 shop, I suppose) but the range is just dandy - drops from "very good" to "good" at about 30-40m in an open field, with the MiFi inside the car. Also the three-button problem is solved by downloading a firmware update to allow you to use the web broswer interface to select "auto" connect mode, so just a press of the power-on button is required. However, this still requires manual intervention - there's no way of having this device come on automatically with the car ignition.

... need 802.11n support anyway? The maximum speed advertised for this service is 3.6Mbps, below even 802.11b's 11Mbps, let alone G or N. Increased range is the only relevant benefit that springs to mind, and given the implied increase in power requirements ...

Maybe it could beep - or your PC could - when you haven't used the network for some minutes.

Most of the phone deals I see advertised don't have tethered data access - Internet using phone applications only.