I recently bought a Samsung P2370HD to use as a second monitor with my MacBook. It’s a beautiful display. When I connected it to my MacBook via HDMI (using the excellent moshi adapter), the Samsung was blurry at 1080p, so I scoured some forums to figure out how to fix it.
The answer is simple: set the Samsung’s HDMI Input name to PC.
On the Samsung, go to Menu > Input > Edit Name > HDMI > PC.
Further reading: http://forums.macrumors.com/showthread.php?t=959170