Adding to that, the things a C++ compiler can do at compile time (via static typing and full knowledge of the types) is pretty convenient and impressive, relying on these things to be done at run-time is often complex and/or require more code to be written by the programmer.
If you can live with enabled exception handling (which is a performance toll) then some additional object meta data shouldn't be a problem.
The thing is, C++ is usually good about not charging you for features you don't use - and with the reasonably good debugging and profiling tools, most of the problems you mention above are fixable to get performance that is close (or equal) to C, with maybe better maintainability.
To pick a not-so-random example of something that's difficult to implement in C as safely as in C++, see expression templates[1]. I'd be interested in something similar to what eigen does written in C. (Of course, the last time I did this minibenchmark, so-and-so's lapack library was still slightly faster than eigen :)
The bottom-line, perhaps, is that if I'm writing a library, I'd do it in C simply because it's self-contained and has a nicely limited scope, and as a bonus is usable from oh-so-many other languages. If I'm writing an application that really, really requires serious performance, I'd prefer to use C++.
Can you guarantee that for every 3rd party lib you use?
Since C++ lets you omit language features until you basically have plain C, you get to choose what level of support you can live with.
For example to get a class name you can either use [object className]. Or you can use object_getClassName()/directly access "anObject->class_pointer->name" without dispatching any messages. The same goes for any other runtime attribute of an object.
For big loops, be comforted in knowing that message passing is aggressively cached; the second and subsequent calls are barely slower than a C method call.
And for those insanely big loops, with methodForSelector: you can bypass message passing entirely and call the method directly... you speed freak.