I'm not sure how the math works for 3D games, but I would think that for 2D games, a curved monitor actually reduces distortion.

In a flat monitor centered in front of your head, the distance between your eyes and different pixels on the screen varies depending on how close they are to the edge, thus distorting the sizes of the rendered sprites. Curving the edges reduces this effect (depending of course on the exact curvature and distance to the monitor).

I guess the key question for 3D is whether the rendering engine already attempts to compensate for this effect. It seems difficult for it to do so, since monitor sizes and distances vary so much, but I suppose that's what settings like field-of-view are for.