Summary: Basically motherboard manufacturer's discovered that Ultra is SLI with SLI disabled and created several motherboards which would allow running SLI with cheaper Ultra chipset. nVidia didn't like it and disabled it in newer driver versions. Anandtech compared the two chipsets and noticed that if you connect two resistors - Ultra turns into an SLI and bypasses driver restrictions.
There are also comparisons between 16x (regular), 8x/8x (normal SLI) and the Ultra SLI of 16x/2x. And the latter option seems to be just slightly behind regular SLI.
What I'd like to say about the article is that they forgot to mention that they don't really know if it would be possible to make Ultra work with two fully functional 16x slots, or 8x to be exact. It can be seen that the 2x slot is a problem for fully functioning SLI already and it will only grow if nothing is done.
Another problem is that nVidia will hardly like the idea no matter what and we might end up with rising prices for Ultra or new protection methods.
Regardless of how it may turn up, this is an interesting development, and I am looking forward to new developments in this area.