I have some questions:
1) Whats the importance of Dual Link DVi?
2) Do all nVidia and ATi cards now have Dual Link DVI?
3) Is it comparable to HDMI?
If I understand your question correctly I can tell you what little bit I know.
1) Dual Link DVI allows you to set up use to separate monitors with both monitors connected to 1 pc. I have a 25" and 21" monitor connected to my new build pc. This allows me to work on 2 separate pages or projects side by side. Like I can search the web on 1 monitor while watching Live Tv on the other monitor.
Bascally to me its almost like having 2 pc's.
Older video cards have 1 VGA port out and DVI port out.
"most" monitors have 1 VGA port in and 1 DVI port in. when I was shopping for a new monitor I wanted a monitor with 2 DVI inputs. The few monitors out there with 2 DVI did not impress me.
On my 25" monitor I have 1 pc connected to the DVI port and another PC connected to the VGA port. With a button on the front of the monitor I can switch back and forth between 2 separate pc's.
2) No I do not think "all" cards have Dual Link DVI. Most of the new card do have 2/DVI.
3) I have not tested the theory that DVI is comptable to HDMI. But I have seen on newegg.com
dvi to hdmi converters and I have a dvi to vga converter that is in use.