I worked more on Squeak today. In particular, I went through one of the tutorials that has you actually write smalltalk code (rather than just using the eToys interface, where you drag and drop elements to script the behavior of morphs -- the graphic elements in Squeak). I had a good experience showing Charlie how the eToys interface works last night, but I'm concerned about the bridge between the eToys interface (which is reasonably friendly) and the smalltalk development environment, which is about as friendly as twm (Tom's Window Manager -- Take a look at 
some screenshots).
OK. It's friendlier than twm -- but not by much.
My question is which environment will let students get farther over the course of the semester. Squeak has the eToys interface, where the learning curve (with just a little guidance) is extremely low. On the other hand, the real power of Squeak comes from the Smalltalk interface and its not clear to me that using the eToys interface will help you learn how to do that. Netlogo, on the other hand seems harder than eToys, but is a good bit simpler than Smalltalk. Furthermore, Netlogo is really pretty limited in what you can do -- Netlogo could have been implemented in Squeak and many Netlogo projects could be done using eToys. Once you learn the Smalltalk interface, it's probably just as easy to do anything you can do in Netlogo using Squeak. But I'm not sure which will be most useful for students.
I could divide the class and have half work on Squeak while the other half works on netlogo and see where they get. Or I could introduce each and let the students choose one or the other to do a more serious project. I think the latter is a little more balanced. It won't be a real experiment (or even a quasi experiment), but with a little thoughtful work ahead of time, it could make a nice "action research" piece.
One thing that's been niggling around in the back of my brain is the similarity between eToys and the "cocoa" kids programming environment that was create at Apple (before they started calling the Rhapsody yellow box "Cocoa"). I was wondering if they were directly related to one another, but this paper reminds me what cocoa looked like and I can see it was quite different. I had forgotten how wordless it was. But I'm sure all these people were talking to each other and exchanging ideas.