Namespaces are fully supported. The library has not yet been converted to use namespace std, however, and the old std-faking code is still on by default.
Exception handling is now thread safe, and supports nested exceptions and placement delete.
Exception handling overhead on x86 is much lower with GNU as 2.9. This ABI is subject to change without notice, so don't use it for anything that you don't want to rebuild with every release of the compiler. The basic idea is that now templates are minimally parsed when seen and then expanded later. This allows conformant early name binding and instantiation controls, since instantiations no longer have to go through the parser. In many cases, but not all, the compiler will tell you where you need to add 'typename'.