Haven't got a dongle, but I do have a
mifi, which will operate both as a 3G-wifi gateway and a dongle (if you plug it in via USB). Works very well, no complaints at all. 3's service is pretty good round my way and it's got a battery life of about 4 hours or so as a wifi hotspot (and obviously no battery issues if you plug it in to a USB port, in fact that's how it recharges)
Do they still get shirty about having mobile phones & etc on in hospital wards?. It might be a bit more discreet as you could leave it somewhere out of sight.