The (beta9 documentation for VS2010 is online, and therefor also the Breaking changes in VS2010 C/C++:

• “auto” is now a keyword
• “static_assert” is now a keyword
• Lambda support excludes support for unquoted GUID in an IDL (it uses the same […] syntax)
• Some “.NET-Exceptions” can now only be caught with __try __except
• /GS checks might decrease performance
• Project files are automatically converted to the new .vcxproj
• CRT/MFC/ATL/OpenMP-DLLs no longer use fusion (huray!); it uses plan old dll-hell
• Support for environmentvariable __MSVCRT_HEAP_SELECT was removed
• New _ITERATOR_DEBUG_LEVEL macro (replaces _SECURE_SCL and _HAS_ITERATOR_DEBUGGING)
• hash_map and hash_set are now in the std namespace (previously in stdext)
• SafeInt is included