So I checked out the PBL, Seems it is the old NJABL (resurrected by Samphaus). From what I have read it seems promising. The PBL is the Policy Block List. It includes many of the dynamic addresses that should not be sending email, because of their parent ISP's policy. Many of these dynamic addresses are probably the major source of spam today (Microsoft zombies). I have found several testimonies to the effectiveness of the PBL on the Internet.
Of course it may not be for everyone. But for a small domain such as mine, it may be beneficial.
I already use the Spamhaus combined SBL and XBL. And I see that there is a combination of the Spamhaus zones called zen.spamhaus.org. To use it I commented out the existing sbl-xbl Spamhaus line in the postfix main.cf and replaced it with this line:
As always, I will monitor my logs to see if this new RTBL has an impact on my regular mail.