My biggest disappointment with C++ is that the standard libraries are completely unsuitable for use in embedded systems where you have to control when, where and how many memory allocations occur. This is particularly important when the system level design choice is to perform all allocations at system startup, which is a common design pattern for high performance systems with real time characteristics. A high speed messaging system I worked on ran into this all the time. We couldn't use the standard implementations of things like heaps, hashes or queues because they don't have a way of making memory allocations occur at startup. It was quite common to have to re-implement those data structures when adding a new feature, as the stl or boost implementations were not suitable for this design pattern.