its smooth as hell. i can flick the screen and its like spinning a top as all the screens fly by. there is a setting to control the speed the screens pass by though so dont worry there. Ive used pretty much all of the launchers and have some in my download list i paid for and dont use.
Also keep in mind that if you put an application dock from the stock widgets list on the screen you can drag and drop as many app icons into the dock and then scroll through them. I also purchased an app called Launch-X that does about the same thing but doesnt scroll. you can see it in the pic i posted. the free version limits the number of apps you can load but you can also include contacts in the menu. Its like making your own widget for items you want at the ready without making a mess of the home screen or any other screen you put it on.
YouTube - GDE - The New Home Screen Experience running on Moto Droid