I use a PC connected to my 50" Panasonic plasma, mostly for watching HD movies, with great results. The video card has a DVI output, which connects to an HDMI input on the TV, via a DVI > HDMI adaptor, and a normal HDMI lead (I'm not sure if this connection carries audio - I use a seperate AV amp)
The video card driver (nVidia) allows you to adjust the picture for height and width in case of problems with overscan.