I started doing GTD. I use Calendar for my "hard schedule"—things that I have to do on a specific day and/or time. I use Inbox reminders for my "hey do this if you get the chance." And then I keep my big todo & projects list in Docs. I find they all occupy a slightly different and nice niche—todos & projects in permanent stuff, inbox for "soft time", calendar for "hard time." I find there's a lot of mental benefit to separating these things out. When something is on my calendar, I know that means do it. When something is in Inbox, I know I should just get to it as soon as I have the time and energy. (This works better with inbox zero though; if you have a bunch of other emails etc lying around it dilutes the reminders.)