I passed the IBM 486 exam with 70%.
I should say that the exam was a tough one. I prepared from 4 books - Rumbaugh (OMT), Booch (User Guide), Larman and Fowler giving stress on the latter two.
The forum helped me a lot in passing the exam.
I have one query that Rational has a similar certification examination in OOAD (site info :
http://www.rational.com/worldwide/india/certification_exam.jsp#Length). Now which exam has more acceptability - The IBM one or the Rational one.