Can one just load an image into an non-texture space and then just blit it to the screen with OpenGL?
glDrawPixels
but it is slow, but if all you want to do is show an image it is fine and easy.
If I want to use it to draw some graphics in a game, will it be fast enough or will it slow down the frame rate remarkably?
Too slow for that, although its support/speed is improving, or will improve. At the mo you will have to texture map your image to a polygon/quad.