Yes a JavaScript action is basically wrapped in an anonymous function and then called. The variable scoping then works as you'd expect.
The standard way of passing values between script buttons is via hidden text boxes, copying and pasting as necessary. That can get a little tedious if you do a lot of it. As I said, you can store values in the global window object and access them from any Javascript action, in scripts on different buttons or even on different flavours, so long as the browser window isn't refreshed.
I'll be at many of the Personas related sessions at TechEd - feel free to say hello 
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Steve.