Thread: Using this pointer in constructor

I've read before that using the this pointer in a constructor should be avoided. Generally I can understand that the object may not be entirely constructed yet, but I've never understood entirely what the potential issues are.

This SO thread mentions:

"'this' should not be used in a constructor anyways unless you know what you're doing and don't mind the limitations"

(They also deal with shared pointers, which I should be doing...)

This cboard thread doesn't really have any bad things to say about the practice.

In some test code, I didn't as much as get a warning from the compiler:

Code:

// thistest.cpp

class A;

class B {
public:
B(A *a);
private:
A *a_;
};

class A {
public:
A();
private:
B b_;
};

A::A()
: b_(this)
{ }

B::B(A *a)
: a_(a)
{ }

g++ version 4.6.3
g++ -Wall -c thistest.cpp

For something more concrete, I have a Model class, which is more or less a fancy symbol table. I don't want to give all clients full access to the model, so I created another class, ModelReader. ModelReader can return a requested symbol from the Model, but can't do much else. I would like it if a Model could provide its own ModelReader.

Code:

#include "modelreader.h"

class Model {
public:
Model();
ModelReader *reader() const;
//And some other stuff
private:
ModelReader reader_;
};

Model::Model() {
: reader_(this)
{ }

ModelReader *Model::reader() const
{
return reader_;
}

Code:

// modelreader.h

class Model;

class ModelReader {
public:
ModelReader(Model *model);
// Some other functions here to make it useful
private:
Model *model_;
};

ModelReader::ModelReader(Model *model)
: model_(model)
{ }

Are there any limitations to this approach?
Are there better design alternatives?
In general, what are the limitations / caveats to using the this pointer in a constructor?

Thanks in advance