Just a clarification: it is possible to go online over ad-hoc, but the host computer must be connected and have the "share internet connection" box checked in settings.

Also, at least one commercially availible wifi here in Shanghai appears to be open, but you cannot use it without paying for it. Still connects though, just like described. I've noticed that all connections that actually work will go from 'connecting' to 'connected' within a few seconds, the others take quite a bit of time.