Eating the dog food.
It took me a while to make my decision and one of the reasons I chose to accept the offer was that I used so many of their products. At the moment I finally decided, I realized I had 5 Google properties open at that time.
However, I've avoided using Google Calendar, Docs and Spreadsheets for a while now. I've had a number of good reasons to do so, but for some reason a flip switched when I signed that offer letter and I'm eating the dog food (interesting Wikipedia entry by the way.) I'm trying to use both for 2 class projects this quarter.
And yes, everyone to whom I've complained endlessly about Gmail: that's my primary non-school email id now, and I really like it; no seriously, really!
I also find that I have a very, very different perspective when I read articles like this one.:)