It's certainly useful if you're somewhere foreign so can't really hotspot.

In my case my Nexus 7 is sat somewhere in the room with better signal and I'm connecting with my phone. It has been a bit flaky but I think that's due to the poor wifi. Certain apps don't work though due to it not being a conventional connection.

Yeah that's right. I think it's apps that check if there's WiFi or 3G and if not they refuse to admit they can get connected.