Thanks guys, this was quite informative... I keep my action lists as lightly structured plain text files (i.e., digital, but tool-agnostic), so I'll have to adjust things a bit (e.g., "tagging" is not really available, so getting alternative views of set of tasks is not easily possible).
I like the description of using GTD to "fill your mind" after it is been emptied! I think I have evolved something similar actually in past month or so without realizing it... but have stopped and forgotten about this. What I did was establish working "dashes" throughout the day, and for each dash I'd prepare a separate, short task-list, by cherry picking the most important or appropriate tasks from action lists. When executing I only looked at this list... once it was completed, I'd start the next dash & selection process again.
Hm, maybe the answer is I should just put more effort into running things this way... results so far are quite promising.