I'd like to know some of the answers to your questions as well.

I tried the "activities" approach with the RC2K
MK-I (a device based unit) and got real close. But because I had to rearrange so many "screens" the stupid thing ran out of memory.

Another important thing to get these remotes to work just like we wish to use them is to not treat macros in any special way. They should not have to say "Macro" on the button, you should not have to hold the key different to execute them, you should not have name or button shape restrictions, you should not have number of macro restrictions and you should not have to go to special pages.

It appears from what people have described that the Pronto could be activity based but requires a lot of rearranging like the RC2K did. The fact that Microsoft considered this from the start is impressive to me.