Deterministic Finalization

I don't quite get what all the fuss is about with not having DF in managed code.
I mean if you can do this:

void fooplusplus()

{

  ... // do stuff

  ~someobject();

}

why would this be any worse?:

void foosharp()

{

  ... // do stuff

  someobject.Dispose();

}

Besides from having to implement the IDisposable design pattern and fleshing out the Finalize code, I don't see how it could be so bad.
Besides which of the following is worse:

void fooplusplus()

{

  ... // do stuff

  // I forgot to do this

  //~someobject();  

}



void foosharp()

{

  ... // do stuff

  // I didn't know I had to do this

  // someobject.Dispose(); }

UPDATE: as I'm reading more about DF in C++ I'm seeing how it's practically used and now it makes sense. I guess I just don't see why .Dispose() is so bad.