You're right. I'm a Firefox user and hadn't noticed that it won't work. You can get Slingbox.com's Watch feature to work with Chrome, but you have to use IE Tab to do it. That won't work on Google TV, I'm sure.
Here's an interesting thought though... I use Sling MobilePlayer for Android on my Eris. Since Google has alluded to opening up the Android Market for use on Google TV, I'm wondering if the .apk for MobilePlayer would work? Think it would be the correct resolution?