I think a 24" is fine for everything, and personally I feel a 27" is way to big for anything. HD and BR movies may look good, but SD or below SD standard movies will look awful in full screen view. There is a difference between TV and Monitor, so if you are thinking things will look good on monitor as TV then you are making a mistake.
My eyes were fine; I guess I did pump the brightness down a bit because it was a bit obtrusive - I need a 27" (planning on buying one within a month) for university as my desk is away from my bed and I love movies so I want to see the screen. I have lots of blurays and only really watch 720p-1080p and play in 1440p games so there's that!