New spreadsheet, should you keep renting or buy a home?

I put another spreadsheet that I had made a while back online as a Google Docs template. This one is "Should I keep renting or buy a home?". Simply enter some numbers and estimates in, and it will tell you whether it makes the most financial sense to keep renting or buy a new home. See it at https://docs.google.com/spreadsheet/ccc?key=0Al_XAoAHsV3edHJWYXdSN1ZhY015UjU5aFF4eDJpeVE&hl=en_US