Jenn, over at Pocketables.net, has explained in step by step instructions how to tether her AT&T Tilt (WM6) to the Nokia N800/N810 Internet Tablet.
Although various hacks and utilities exist to enable the functionality, I didn't have to use any of them because the Tilt actually supports BT DUN right out of the box. Or at least it does after all the AT&T nonsense is wiped off. (Given that AT&T buried Internet Sharing and put Wireless Modem in its place, I wouldn't put it past them to have somehow disabled DUN too.)
Unfortunately, just because the functionality is there doesn't mean it automatically works. The main obstacle when trying to establish a BT DUN connection between the Tilt and the N800/N810 is that Nokia's predefined operator settings aren't correct
Head over to Pocketables.net and see how it is done!
Source: (and photo credit) Pocketables.net