I may not have complete answers for your question but here's something i understood from the developer FAQ
Question 1:
First things first. You should read the Developer Guidelines section. (Of course you must have read it) and create your site considering all the design guide lines. The Navigation part is crucial! You should be able to let the user navigate with arrow keys (directional pad) :)
To test your application, the closest you can get without a REAL TV is Chrome web browser it self ON Linux :)
The browser on Google TV is simply the
Linux version of Google Chrome. While
the user interface is modified
slightly for the TV form factor, most
of the rendering and web platform
capabilities are consistent with
desktop versions of Google Chrome and
you will receive the latest updates
automatically
Another question in the FAQ is
Q. Is this yet another browser platform that I need to test my site on?
A. Google TV utilizes Google Chrome as the browser, so most websites that function in Google Chrome should operate correctly on Google TV.
So if you design for the
- 1280x720 resolution. Recommended
width is 1152x648.
- 1920x1080 resolution. Recommended
width is 1728x972.
resolutions and if you test it on a screen with the above mentioned resolution (A lot of laptops and desktop monitors support this resolution) and if the user can work fine with it on Chrome 5.0 on Linux (using directional pad), I think you are good to go :)
Question 2
In my opinion, the sound would be OK as long as it is not ear piercing and disturbing. Simple short sounds when the user hovers over an icon to provide audible alert would be really helpful and a really nice smooth sound for the splash screen would add a dramatic effect BUT the user should definitely be able to mute the sounds. I think this wouldn't be hard because Flash is supported :)
Question 3
This seems to have some design guidelines for the designing UI's for TV
http://en.wikipedia.org/wiki/10-foot_user_interface
and Kylo is a a web browser for the TV!! Check out it's features.
http://techcrunch.com/2010/05/24/google-tv-and-optimizing-the-web-for-the-10-foot-experience/
Maybe you can get an idea about it :)
Question 4
Well i cannot answer better than the http://www.google.com/tv/developer/ website :)
But confirming to the usual HCI design principals and usability goals wouldn't hurt anyway and would go a long way :)
Check out these websites too if you haven't already
http://www.sonydeveloper.com/
http://www.logitech.com/en-us/1005/7099?WT.mc_id=google_googletv_redirect_052010
http://www.intel.com/inside/smartTV/
http://www.dishnetwork.com/googletv/
Hope this helps you in some way :)