Well, didn't take an hour - about 3 minutes, been playing with it for a few minutes now. Have DVD player running watching "The Wild" on the 55", while I'm typing this on the laptop. It looks pretty nice.
The dvi to hdmi cable does work here. My 55" is a 720p TV.
Important**** - One thing you need to know - with an HDMI connection to a TV - you must turn on the TV before you boot the computer. At this time there is still an issue with the way HDMI passes it's info to a computer due to no standards really having been set within the industry. If the computer is turned on first, TV's will sometimes refuse to pass resolution info, etc. required by the computer to initialize that display.
A lot of the info related to connecting a computer like this is very hard to find, as there are just not a lot of people doing it yet. Mostly, you will find problems out there with no solutions. At this point it either works or it doesn't. And as I said before, there will be no luck with Linux at least on a system that uses a BIOS, may have to try Linux on this board to see what happens.
Once you are connected and up and running, you will need to go into System Preferences - Displays: You will more than likely have to reset the resolution for the laptop, mine booted up in 800 x 600 mode. And you will need to set the resolution for the TV screen. When you get into Display, there will be one on your LCD and a separate one on the TV. It will initially have the TV on the right side of the monitor - so just move your mouse off the right side of your laptop screen and this will move it onto the TV screen.
You may also have to play with turning on and off overscan in Display properties on the TV and also adjust the overscan options within the TV's menu if you have those options available on your set.
On the TV Display options on mine under the Color tab is a calibration option. Would recommend running that also.
PS. You may not have as many options in System Preferences with the onboard video. And it may not have the ability to keep your laptop display running at it's typical resolution and out put 1080 to the TV. You may have to reduce to the ouput to the TV to 720 which it should accept fine. Let me know how it goes.