The document “Technical Performance on C++ Performance” is a good read if you are really interested in the advantages/disadvantages of using C++ on an embedded platform.
The Embedded C++ Homepage is sort of a hub for embedded C++ programming. They define a sub-set of the full C++ language for use on embedded devices such as microcontrollers.
C++ Standrad Libraries For Embedded Devices
uClibc++ is a C++ standard library designed specifically for microcontrollers. It even has exception support!
Check out The Standard Template Library (STL) For AVR With C++ Streams if you want to get a library for using things like string and iostream with AVR microcontrollers.