Did anyone see favorable results?  If be curious on folks experiences. 

A little on some of my sites, but I do notice a lot of posting with bad email addresses which bounce, mostly spammers.

I disabled it because of to many spammers.

Is there any option to check stats of PBR option? Can We check how many post was added via this option?

I don't know the answers to these questions, but I turned on my PBR. I still manually approve registrants, and when I do, I'll probably find out immediately who the spammers are. I've approved some members since I activated PBR not too long ago (like a few months), and so far no spammers. I'm surprised none have joined and posted before registering. Then again, I finally turned on the spam prevention features. 

Then again, maybe they have, but I deleted the obvious spammers immediately, so I never saw their spam. 

One thing I do when I notice spammer coming from specific domains, I ban the domain and it prevents them from using those email addressed on PBR. The form does use your site ban list I believe, but I'm not sure it uses IPS spam services to prevent registration. Maybe @bfarber or @Matt would know for sure how it works.

All accounts are ran through the spam service during registration, but not before.

8 hours ago, AlexWebsites said:

The form does use your site ban list I believe, but I'm not sure it uses IPS spam services to prevent registration.

In my case, I simply meant that if the registrant got a "4" from the spam service instead of a lower rating, I deleted him. Thus, if he had posted spam before regestering, I never saw it.