Yes, if you login to your account online you'll see the is a box on the main page for redeeming a prepaid card. All you do is enter the code on the card on your account will be credited the face value of the card. Yes you can add as many cards as you want to redeem. You could also do this on the phone when you call them about renewing your subscription at a better price, but some of the reps don't seem to know about using prepaid cards. Their playbook is geared strictly to credit cards or invoices. So better to have the money in your account before you call.
Using a prepaid card does 2 things: One, it keeps them from having your credit card number on file so they can't automatically bill you at their exhorbitant retail rate. Teo, it saves you from having to pay a $2 invoice fee if you don't use a credit card.
As for is it better than other streaming services, probably not. It's more convenient, since it's built into most cars today, But so is Pandora, which is free (with ads).