We talked a little about it
here, but we mainly spoke about the orbital wheel.
Manchild presented
here a similar (more complicated, of course!
) tire he patented.
I presented several new ideas for spherical wheels you may find interesting
here.
Finally, I googled around a little for updates, that is what you are asking for. I found only references to tests (latest in April/2005) at mini-loaders at the (I cannot believe it) colombian Michelin site:
The tweel won a gold medal at Intermat (I have not the slightest idea what it is) in 2006. However, I could not find the price for tweels anywhere...
The french Michelin site has no results for a "tweel" search.
That does not look very promising.
Anyway,
I do not want to have to clean the mud from that thing. I'd try to fix some walls to it, but I guess it would make the tire more expensive.