Hey there,

are you using an ATI graphics card?

It's a little quirk with some ATI cards that the render view seems slightly anti-aliased regardless of the settings that you use.

It's not the end of the world though, you can zoom in (as you've found out already) to remedy this while inside Maya and when you save the file or do a batch render the images will be fine.

I have no idea why some ATI cards have this issue but at the end of the day the render view is only really used to inspect, often zooming in any way, what you will eventually save or batch render and as the final output is perfect there's no need to worry.

Take it easy,

Mat.