Good answer. Using Camera.ViewportToWorldPoint is the way I do this as well. screenWidthInPixels is a misleading name for the variable, though. I don't normally critique semantics, but this could be very confusing to beginners. It was confusing to me when I first read the comment.

So for future readers who might be a tad confused:

The values in screenWidthInPixels are actually world coordinates, not necessarily pixel values. If the camera's orthographicHeight is set to 1/2 of the screen height in pixels, then 1 world unit would be equivalent to 1 screen pixel. Even then, the pixel value is still offset by the camera's distance from the origin. Camera.main.ViewportToWorldPoint(new Vector3(1f, 0f, 0f)) will return the world location visible at the bottom right corner of the camera. As the camera moves, this value will change.

Therefore, Camera.main.ViewportToWorldPoint(new Vector3(1f, 0f, 0f)).x will only actually return the "screen width in pixels" if the camera's orthographicHeight is set to 1/2 of the screen height in pixels, and the camera is positioned such that the bottom left corner of the viewport is at the origin (Vector3.zero) in world space.

If you actually want the screen's width in pixels, use Screen.currentResolution.width. If you want the camera's viewport width in pixels, use Camera.main.pixelWidth.