If you search the forum you'll find that extended warranties have been discussed several times fairly recently.
Some owners like the peace of mind that they provide against catastrophic/expensive failures. Others worry that the warranty companies hide behind too many exclusions and/or think that the money could be better used/invested elsewhere.
And of course, like the hotels in Las Vegas, the warranty companies always come out ahead.
Here is a good thread to get you started:
http://986forum.com/forums/general-discussions/29955-boxster-warranty.html