When it comes down to it, you just have to do what works for you. But I should say that just leaving the list in the notes of the project has a couple of disadvantages.
One disadvantage is that you lose the context of the lists. Your lists are titled "@calls" or "@computer," because you don't need to be thinking about all of it - just think in the context available to you right now.
Another issue with only using the notes is that you now have to open a project and review the notes every time. You can save yourself the time of reviewing each project for appropriate actions, by breaking it out. My experience more often has been that people get stuck, because their next actions are out of sight and out of... Think of how many clicks or keystrokes you require of yourself just to see your next action.
It could be worthwhile to update in the notes and keep next actions on context lists. The double entry is minimal. You might have a list of actions in the notes where you keep a tally of completed actions and expected actions, but that should supplement, not supplant, your next actions as individual items. You could do something like:
* [03/21/05] Action foo
* [03/26/05] Action bar
* [?] Action foobar
If you use dates in the brackets, rather than 'X' for complete, then you also have a quick way to look up the completed action and any additional notes. That's a handy tweak if you're into it, but I would just start with the basics of a project list and next actions in the context lists. A big part of GTD is keeping it simple enough that you don't have to interrupt your workflow to prune the system and tweak every cranny.
Hope this helps, John. Let me know what you find that works and what doesn't, because I know some other people who are trying to work this out in their system.