I usually play on my monitor there's nothing stopping me playing on the TV via HDMI at 1920x1080 with my surround sound through optical but for some reason my 22" pc monitor with sennheiser headphones is much more immersive
Depends on the mood I am in and the type of game. I have been alternating between using my 40" Sony and 22" monitor for Deus Ex: HR. Some days I just feel too tired to sit at my desk so opt the TV route.
I will say one thing though, and that is Deus Ex: HR works very nicely with a controller + HDTV + PC setup.