(Note that Smalltalk is a "pure" OOPL, and C++ is a "hybrid" OOPL). Before reading this, please read the previous FAQs on the difference between C++ and Smalltalk.
The "purity" of the OOPL doesn't make the transition to C++ any easier. In fact, the typical use of dynamic typing and non-subtyping inheritance can make it even harder for Smalltalk programmers to learn C++. Paradigm Shift, Inc., has taught OO technology to literally thousands of people, and we have noticed that people who want to learn C++ from a Smalltalk background usually have just as hard a time as those who've never seen inheritance before. In fact, those with extensive experience with a dynamically typed OOPL (usually but not always Smalltalk) might even have a harder time, since it's harder to unlearn habits than it is to learn the statically typed way from the beginning.