Extended Warranty Question

Just picked up our Prius yesterday after a two week wait. It was already on the way to the dealer so that's why we got it so quick. Two things I have never done before in buying a car is pay MSRP and get an extended warranty. They wanted $1550 for the warranty and I said $1200 was more like it. I knew before hand you could get it for around $950 other places but I need to have a good relationship with the dealer.
I bought the warranty because I plan on keeping the car for 100K miles or 7 years. This car also has very few options on repair except a Toyota dealer and they are not inexpensive.

My questions.

1. Has anyone ever had to use their extended warranty on their PRIUS?
2. What problems have PRIUS owners had on the 2006?
3. What does the extendend warranty buy me the first three years?
4. Should I have waited till the end of the 3 year period to get the warranty?