Higher resolution does improve your image quality quite a bit, but it's not the whole truth. Most games are created with a lot of different textures, and if you set your resolution to 800x600 16bit and step close to a wall and only look at the texture itself, you probably wont notice any difference if you bump up the resolution to 1280x1024. When you switch to 32bit color things start to happen, now you should definitely see some improvements. If you now switch the resolution back to 1280x1024 you will notice how the jaggies are reduced and become smaller. However, the jaggies are still there, even though they are smaller.
High resolutions do also most often result in a big performance hit.
Now when the card is actually released, we can all see that it's possible to do almost the same in real time gameplay. What FSAA does is that it softens all the jagged edges of textures on models and so on. The cool demo that often comes with the package is specially made to overwhelm you with reasons to buy the product. Don't fall for that - it's just a demo. All rights reserved.