Having participated on April 3rd at the Apple store and then again today, I wholly agree! Things went very smoothly both times. It definitely made a difference that people were able to preorder and also for the April 3rd launch reserve an iPad for in-store pickup that day, with controlled time period and separate lines. It also helped things to move smoothly when Apple did the necessary iTunes update a couple of days in advance, too. I think they learned their lessons with the various iPhone launches...NOT a good thing to launch a new product which needs to be activated AND a whole new service (MobileMe) at the same time!
Looking at this, I see that presenting the iPad in two separate launches also undoubtedly put much less of a strain on people and servers than if all the models had been available on April 3rd. (Not to mention the other potential advantage for Apple: people purchasing the WiFi version and then deciding they wanted the 3G version instead or in addition ....)