Well, keep in mind that with a 13 you will have to pay nearly 100% of your disposable income into the plan. The plan is not designed to leave you with "extra spending money" every month, and as others will attest, it leaves you with very little to live on. Depending on your income and other factors, you might end up repaying 100% anyway.
Regarding the Consent to Judgment -- I use these all the time. The benefit to the creditor is that if you default on the payments, they can go right in and enter a judgment -- ie they don't have to waste time serving you summons, arguing at trial, etc.
How does that benefit you? Well, there's usually a monetary benefit to you. First, if they have to spend time serving you and litigating at trial, those legal expenses and court costs get tacked onto your balance. Plus if they have to go to trial, they'll seek the full balance.
I usually offer my customers a settlement as enticement for them to sign a consent. For example, they might owe me $2500. My conversation would go something like this: "If you agree to the judgment and payment order, we'll draw it up for $2000..... If you don't want to sign the consent, then we continue our lawsuit, in which case we seek $2500, plus court costs of about $334.54, plus attorney fees of at least $350. So if we have to go that route, we will get a judgment for roughly $3200. And so it saves you about $1200 to sign the consent form."
So like I said, there's usually a monetary incentive for you to sign it. I have lots of customers sign them, and as long as they pay as agreed there's never been a problem. Keep in mind, though, that if you don't pay as agreed, then they can automatically enter that judgment without going to trial.