Currently, the auto resize of the the columns does not take the width of the grid into account. I don't think this is how most users would expect this to work. The autofit of the columns should be able to resize the columns so that they work as best they can within the grid's bounds.
Now, when I autofit my columns, the first thing I have to do is resize the columns manually so I can see the whole row on the screen. Since I end up resizing the columns manually anyway, autofit ends up not really helping me much.
Some toolkits I have used have a resize mode for a table which determines whether or not all columns are to always be visible or not. If all the columns are to always be visible, resizing one column needs to resize the others so that everything still fits. This "mode" could determine which algorithm autofit should use