I have seen these on Ideal World before now and simply never been convinced by them. Since introducing them, they've been flogging them with ever more generous terms, like unlimited net access for 2 years. Sounds good, but also stinks of desperation.
It's "free" internet is retrieved over the now ancient GPRS technology. The reason it's still competitively speedy is because Datawind's technology compresses the data content of what you're looking at. They say this just makes it faster, but in real life this means that images and visuals are going to be compressed and thus lower in quality. This is true of any form of visual asset compression, because if it wasn't, then all internet providers would use data compression to "speed up" their networks and manage bandwidth usage.
The device is relatively low spec and low colour depth screen. If you just want to use it for emailing or reading text then maybe it might be a good value proposition, but otherwise I doubt it.