I think these days the ABC's are not that important to real estate clients.  
 
Owner, QB

Broker or Broker Associate.  The public knows that word they don't know gri, abr, etc.

I think my CRS has been the most beneficial and continue to receive (and give) referrals. 

To the consumer, unfiltered, these ambiguous letters represent the vanity of Realtors. It is the suggestion to the consumer that a river of more meaningless jargon follows.

HOWEVER, if ONE disignation is used to promote your value position to a specific audience (i.e. distressed real estate and CDPE) there can be value. But that is not what agents do, they append everyting in the soup can to their name.

Agreeing with @Michale Setunsky, BROKER is a designation that implies value to the consumer and HAS resulted in business for me.

Gary Mellott In my opinion being a broker is the only thing that has creditibilty with consumers.

perception becomes reality in real estate, and I truly think that none of the designations do anything for business except relay the thought that you are very well versed in real estate... I had 9 of them..... no one knew what they meant, but as a group, the display of them worked well for me .... 

I have obtained many certification but consumers are not impressed. For professionals, my CPM (Certified Property Manager) designation provided opportunities.

My most valuable credential is my Juris Doctor degree from the University of Virginia.

Good morning Gary. At one time I had my walls filled with designations and certifications and through them all out, as it really has no meaning to your clients. Give me that I am respected and trusted by my clients is important to me.