I don't have the Sony you mention, but I have my PC hooked up to my 50" A10 via VGA.
I was looking at / dreaming about the new 60" 1080p Sony. After doing a little research in the owner's thread, it sounds to me like 1360x768 is indeed the max that the VGA input will accept. If you want 1920x1080p, you have to use HDMI + Powerstrip.
That seems asinine to me on Sony's part. One of the reasons I chose my A10 was so I could get rid of Powerstrip and use my TV like a giant monitor with standard PC resolutions. In a perfect world I'd be filling the whole screen with 1:1 pixel mapping, but I can live with sending 1280x720 and getting the 2" border. However, I'm definitely not going to buy a 1080p TV and then hook up a PC via VGA and get 1360x768 with an 8" border. I don't know why the VGA port is even included under those conditions. I'm not thrilled with the prospect of going back to custom resolutions either, so I've just gained a new level of satisfaction with the TV I have. I'll wait for TV and PC mfr's to get their act together and make this a plug-n-play effort before upgrading to 1080p.
I don't know anything about the Samsung, so I can't address that.