I got this working using my iPhone 4G. Works great. I've only tested it quickly in preparation for some upcoming spring/summer roadtriips... it was pretty simple. I think I just had to connect the phone through USB and turn on the tethering feature on the phone. Then I was able to use another device to connect to the Sync's hotspot and surf.
If anybody wants I can post detailed instructions... but I'm sure there must be some on this forum already.
Brian.