Yes. The screen will run at its native resolution. I have a 21.6" Samsung 216BW running off my macbook. It has its native resolution. I have a desktop/portable set up right now. Apple keyboard and wireless mighty mouse and the screen.
You can even have your screen on your laptop open and use the extra 13.3 inches to drag things over to if you want some more room.
So in total, with my screen open I have almost 35" of surface. Good set up.
...and I wouldn't get an Apple display. Over priced and outdated technology.
MBP 2.4 GHZ
iPad 32Gb WiFi+3G
iPhone 4 16GB
Macbook Pro 13" 2.26GHZ
iPhone 4 32GB
iPod Touch 32GB