On low graphics settings you could probably maintain 30FPS at 1080p. However, going in to any high action areas would probably see you drop to below 20FPS. I would not consider that remotely playable, but it may be OK for you.
Hi there! again :)
Just a quick one to start. Can you run dxdiag and post the text file in here so I can take a look at your hardware specs, drivers etc?