Now, I know what some of you are going to say. "But Boooooob! We can pay no interest for six months! It is like free ponies!"
Yes, except that they are very tiny ponies. You buy some books on Amazon for $100 and defer the payment and interest for six months. Big deal. What are you saving? The theoretical $2.50 you could have made investing that $100? And now you have yet ANOTHER loan to monitor, and if you miss one payment, well, the interest, at 19.99% accrues back to the date of purchase. This will be more than $10 in interest, at the very least.
Just walk away from baited traps. You are not "missing out" on great deals. You are risking your financial life.
If you want "Savings!" then SAVE YOUR MONEY - not SPEND it!