My wife and I set a time to sit down each week and review the scope of our lives, family, and work worlds so that we're in sync with each other. Because we haven't met in a few weeks due to a myriad of activities in our lives, we met for 5 hours today at Starbucks doing thorough individual Mind Sweeps and then a major calendar and Projects review. The sense of relief was palpable when we got into the car to finish some errands!
We have separate GTD systems but a unified willingness to sync with each other each week or so to keep things in harmony.
GTD: Because It Works!