You might want to check the small print on that, I'm pretty sure if you do the no interest payment plan you can't pay it off sooner than the 3 years, you have to go the long haul, they are hoping you will be late on a payment and then they will ding you for all the interest!
Not true. There is no penalty for paying off the 36/24 month no interest promos early. You can make your payments as large as you would like.