I use some minor adaptations, but no major "breaks":
1. I keep one "phony project" for each Area of Responsibility, where I keep my single actions for that AoR. All real projects are also tagged by AoR. I have no single actions. All actions have an informative "project" designation visible in my list.
2. I use a not-strictly-sequential approach to projects (usually a few active actions per project). This is actually in total compliance with the basic definition of what a Next action is (or Waiting, for that matter) but it conflicts with the conflicting recommendation to only pick one at a time.
3. I use priorities and review frequencies in my own special way (as "synonyms"), but not in a way that is at odds with the GTD "spirit". For example, my task selection is fully situational (based on all four types of characteristics). And my Normal (Medium) review frequency is as per the standard.
4. I do not use the original sample contexts, such as computer etc. I have my own. (Don't we all?)