I am a success story of PFL. I received PFL, provided the information and was approved for PR.
But you should understand that it depends on the seriousness of your mistake and where you are located.
The general rule is this:
1) If you are located outside Canada, probability that you will be approved is low.
2) If you are located inside Canada, probability that you will be approved is high. But hire a lawyer who will help you compose a cover letter. In addition to that you should provide a statutory declaration. Every document should be signed and stamped. A lawyer knows how to do it. Don't save money on a lawyer! It's a serious thing.
Also:
1) If your mistake is serious (you hid criminal punishment), probability that you will be approved is low.
2) If your mistake is not serious (you forgot to mention about visa refusals), probability that you will be approved is high.
Remember PFL is not a verdict. It's a chance for you to explain whether you made mistake or you misinterpreted information.
You are welcome.
I'm writing this message for the future generations to help them because I was stuck and didn't get proper help anywhere. Good luck everyone! Welcome to Canada!