I've got a PC connected to a 32WL56 and here's what I've found:
With PC set for standard HDMI 720p mode output (1280*720), the HDMI image cuts off about 5% or so either side of Windows' display image - ie, we lose parts of the taskbar etc. Curious, given the panel has plenty more pixels to play with for overscan etc. HDMI picture quality is superb, if you don't mind guessing what's in the corners
The latest ATI software allows for a custom 720p resolution at 1152*648, which fills about 90% of the panel area, leaving a black border, so I guess we can take our choice from those two, or mess around with powerstrip until we're tired of it.
One thing to note - with the HDMI signal active in 720p, the VGA connection produces rubbish - either a mucky, colour-tinted picture or a blank screen which keeps switching mode. I suspect this is down to the PC not really being capable of properly outputting both together (video card is a ATI 9600 and there are known issues with the things on HDMI). Also can't see anything on HDMI until Windows starts up, but that's definitely an ATI failing and the BIOS screens do show ok on the VGA.
If you need to, the Tosh will take a 1080i HDMI signal (1920*1080) quite nicely, although text readability isn't great as you'd expect with that much scaling-down going on.
With the VGA connection alone, TV handles its 1366*768 native resolution happily and the image quality is very good.
If I can help by trying anything else, feel free to ask - when I get time, I'll play some more. Am also about to contact ATI and Tosh support about the overscanning/black edges situations, so if I get a fix, I'll post it. Or possibly, I'll just buy a NVidia card for the media PC and chuck the ATI!
Jeff