Just started using GTD about a month ago. So far I am very happy with the way it's been working. Clearly though I have lots more to learn.
One thing that's happened is that my NA list is getting quite long. The work list alone hovers around 70-80 items. Most are truly NAs, a few are just "waiting for's" and "agenda" items. The problem is that I am getting a bit "numb" (to borrow a Dave Allen expression) to the list.