If your running at a high resolution, and using AA to see if there is a difference it may not be easily noticed. Try turning Mip Mapping and Texture Quailty to highest, then retry them at lowest, you should see a far greater difference in the texture quailty. Will confirm its working as expected.
Or lower your resolution to as low as you can, then try with AA on and then off the difference will be easier to distinguish then at a lower resolution.