As a mod I could always edit the thread and add a survey. Who says yes so that our OP can see a bit more graphical responses? Great suggestion Hyperion.
I did purchase the extended, but I didn't do so blindly and knew that any kind of extended warranty is nothing more than an insurance policy. I also acknowledge that in the world of insurance, the insurer is usually the "winner" and the insured is usually the "looser". Sure the insurer has to pay out every now and then, and the individuals that make claims are covered and things turn out ok for them, (yes, oversimplification) but on the other side of that, most of the insured will never make a claim or make few claims and as such never receive the full value of the insurance. Homeowners insurance is very much that way as most of us will never make a major claim in the entire time we pay for homeowners.
However better deals on the Platinum warranty are to be had elsewhere. Please go to another Prius board: priuschat.com. If you search the site you should find a link to a dealer on the east coast which is selling the Toyota Platinum warranty at a very hefty discount. You have the length of your factory warranty to buy into a Toyota extended warranty, but there is no real harm in purchasing now if you make that choice.
So far I have not had a single warranty issue with my Prius. I have had 2 recalls... oh excuse me, Special Service Campaigns, done on the car with no problems. From where I stand it is a very solid vehicle. But it is a mechanical device and something could occure in the future, but the car is very trustworthy.
Use your best judgement with the warranty issue and I'm sure you will be fine.