Another approach in 3.4 (don't know if this is proper Ext): You can have a delete handler like this, assuming every row has a 'delete' button.
handler: function(grid, rowIndex, colIndex) {
var rec = grid.getStore().getAt(rowIndex);
var id = rec.get('id');
// some DELETE/GET ajax callback here...
// pass in 'id' var or some key
// inside success
grid.getStore().removeAt(rowIndex);
}