I have an Intel DG965WH motherboard and just recently added the Prolink HDMI ADD2 card. Previously I was running a 30 foot VGA cable from the HTPC to my Sanyo PLV-Z4 projector. Now I'm using a 30 foot HDMI cable.
The HDMI picture is much brighter and sharper than the VGA picture. The colors are better too. Before, I was happy with the VGA picture. But now when I switch back from HDMI to VGA, the VGA picture is noticeably dimmer and blurrier -- like looking through smoke or a gray filter.
The ADD2 card was a snap to install. I ordered online from prolink-usa. It came with low-profile and standard brackets (I had to switch to the standard). It also came with a ribbon cable to connect to the card to the motherboard's audio connector (I'm still using SPDIF to my AV Receiver though). It also came with a dongle that has an S-Video-like connector at one end and component + audio RCA connectors at the other. In addition to the HDMI output, the card has an output labled "S-Video" but it has more pins than a typical S-Video connector and I don't think you can convert S-Video to component with a dongle so I don't think it is really S-Video. It may be component. I haven't tried that connector as I'm only interested in HDMI.
There were no special drivers to install. The Intel Graphics driver automatically recognized the ADD2 card and enabled some more options. Select the "Digital Television" output to output over HDMI. Select the "Monitor" output to output over VGA. Or choose the dual mode to output over both simultaneously. I'm using 720p (1280x720) resolution, which is the native resolution of my projector.
The graphics driver could use some improvements. Sometimes when I turn my system on the display comes up with a shrunken aspect ratio instead of filling the screen. I have to go into the graphics properties and move the aspect ratio sliders from the minimum to the maximum position to fill the screen again. This feature may be there to help with overscan issues but my projector allows me to control the amount of overscan so this feature is just a pain for me. Another problem is that sometimes when I turn on the system, the HDMI output is disabled. I'm suspicious that the computer doesn't enable the HDMI output if it doesn't detect the display device at the other end. And this might happen when the computer wakes itself up to record something while the projector remains off. So I've been tweaking my Harmony remote to try to get it to enable the HDMI output whenever I turn the system on. This involves wrestling the harmony website and learning the hot-key from my Microsoft MCE keyboard, which has been frustrating.
Another gripe about the graphics driver is that while it has predefined hotkeys and you can save a "scheme", you cannot associate a hotkey with your scheme. I hope Intel adds this feature at some point.
Occasionally my display does not update and I suspect this is a graphics driver issue too. For example, with Media Center running, sometimes when I pop in a DVD I hear the audio but just see a black screen instead of the DVD menu. I've found that if I minimize Media Center and then maximize it, the DVD menu will appear and everything will work smoothly from there. I used to occasionally have a similar issue when switching to an OTA HDTV picture -- the display would not show up and minimizing would cure it. But I thought I fixed that problem by adjusting the BIOS settings (Set DVMT to "fixed" instead of "dynamic" and give it 256 MB of memory).
Overall I'm glad I went this route with my HTPC. I think the combination of the G965 motherboard and the HDMI ADD2 card make for an affordable option for HD video. If Intel continues to improve the graphics driver then that will make it even better.