Hi Oleg,
I have had some good success with using sorttype: function(cellValue, rowObject) as you describe. The value which is returned from the function seems to be compared as a String however, and in some cases I would like it to be compared as an int, or date, or some other datatype without having to convert those to sortable String equivalents.
Do you have any idea how to do this, as in how to indicate in the sorttype function how the returned value should be interpreted in a sort?
Thanks,
Nolan