Okay, I was hashing this out and having both interfaces up at the same time doesn't make any sense.

Basically, all I want is something that will allow you to say that two interfaces are on the same logical network and have it use the same IP on the "best" interface, based on, first, link status, and then anything else -- speed, whatever. And it has to be application transparent.

What I mean by that is, if I lose link on my wireless connection with Windows, every long-term connection immediately bombs out, rather than waiting to see if it will regain link two seconds later. I want to be able to be using my wired interface, then unplug to walk across the room and not have any sort of hiccup.