When you use your Paypal debit card it pays you 1% cash back on your account.
This may not seem like much money but when you think of the 0% your other debit cards give you then you can see the cash back start to add up.
You get the benefit of a debit card with the cash back bonus of a credit card. Just be sure to have the card processed like a credit card when you shop at places like Walmart etc. so you can get the benefits.
The important thing to remember is that you must have the funds available in your account in order to make a purchase.
With the 5% interest that Paypal gives on your account you will always make sure you have funds available there.
Enjoy the savings!