You can tell the difference for sure. because the pixels are smaller, things will look less jaggie and require less AA to smooth out.
Now I have a 15inch 1280 x 800(or was it 1200 x 800) screen and it look fine because as you say, the screen is smaller.
Everything is pushing more and more pixels in smaller screens now, so it is just a matter of time before 1920 x 1080 becomes the standard for small screens(cell phone small, its already happening). This does bring up something new, you almost HAVE to be able to scale things now because at that size, my post would be VERY hard to read.
Point in case, I "think" you will notice the difference(if not simply by having more room for programs and being able to see farther on a web page), but if you don't, Your video card will as it will have to work harder(if you game) to render images at the new screen resolution.