How effective are your GTD Weekly Reviews? Running interviews to learn and share

For anyone practicing Getting Things Done (GTD), what challenges do you have when it comes to weekly reviews? How does that compare to others and how can you improve? I'm interviewing folks to validate a product prototype. Happy to share the results here when interviews are synthesized.

Take this 2-minute questionnaire to participate in a brief, compensated interview. http://bit.ly/2MF1mfQ