Great comments all. After having the pleasure of being in the official GTD connect club I learned from ALL the coaches that GTD is really a framework to be modified and adjusted to your needs. GTD is not a religion. The posts here highlight that.
I use Ultimate To Do list synced to ToodleDo & Gmail - more options are appearing, but integrating calendars, task lists and email is simpler by having an account in UTL for Google. They all merge anyway.
My structure is: Goals are projects; Tags include Next Action, Active Projects, xSomeday Projects, Conversations. The tags allow me to start with a list of tasks related to every project (Goals); move things into focus of Next Action and review any correspondence relating to the tasks.
Everything else is in other systems as I am a professional PM and projects be my life.