My PGY2 is in Pediatrics. I am going to take the BCPPS this year and probably let the BCPS lapse at 7 years. Then again, if the next place pays for it I might take the BCCCP (does this make anyone else think Soviet Union?) in a couple years as I am in pediatric critical care. Then I could keep them all and be Pharm.D., BCPS, BCPPS, BCCCP just for the heck of it... or not.
BTW, The letters may not mean much in reality, but an interviewer told me that they like to see the letters on residency preceptor's names on CVs because it gives them an idea of the kind of people you rotated with when they don't have anything else to go on. Speciality letters (BCNSP, BCPP, BCOP) seem to mean more than BCPS, and things like FCCP and FASHP mean even more.