The first thing I'd ask before buying one of these is: Do you have a smartphone which you can use as a wifi hotspot?
I've got a Vodafone PAYG dongle and have been looking at the Go Baby device to use with a soon-to-be bought wi-fi tablet. They look a bit clumsy/brittle if you are out and about so I've not taken the plunge yet but probably will do once I've actually got a tablet. They were £29.99 a couple of weeks ago but the price went back up to £39.99 - never seen them at the full asking price of £49.99.