I've been using a Huawei E585 for several months now, mostly on the train from Robertsbridge to London. This is a cellular 3G to WIFI adaptor (often called a MIFI device). It sits on its own cellular connection and acts as a WIFI base station, meaning it can be used with any WIFI capabale device, eg laptop, phone, internet radio.
Not bad when it works - with a "3" SIM, I can pull 4.3Mbit/s downstream and over 1Mbit/s upstream at good positions.
The problem comes with all the tunnels on the Hastings line - there are two a mile long either side of Sevenoaks and over half a dozen others. Obviously, I don't expect the device to work when there is no signal.
However, I do expect it to re-acquire cleanly when the signal comes back.
The E585 doesn't. Not reliably anyway. On the odd day, I can travel from London Charing Cross to Roberstbridge without a problem. On most days though, the device will lose signal in a tunnel, then get the signal back at the other end - indicated by lots of bars on the display. What it then does is lose its WAN IP - ie loses the IP layer. At this point, it should be making active efforts to get it back. It doesn't. It sits there like a lemon until manually rebooted, whereupon it will come straight back with a strong signal and connection.
This wouldn't be so bad if:
1) I could programmatically reboot the device. So far, all attempts to remote script the web interface have failed due to the particularly weird session handling they employ.
2) They actually issued some firmware updates occasionally;
3) They actually had technical support. "3" don't count, like most cell phone companies, you'll get a bloke in India who asks for a load of irrelevant details then tells you Linux isn't supported - despite the fact it's a WIFI device!
This is typical of so much of the consumer electronics industry where the motto is "first to market, then make the next one".