Steps to reproduce:
1. Create a AdvancedDataGrid containing columns and data, and show it
2. While it it visible, set a formatter on one of its columns
Nothing happens visually. Only after a redraw is forced (for example when it's got hierarchical data by expanding some nodes) the formatter takes effect.
The formatter should take effect immediately.
Workaround (if any):
Changing other properties of a column does force it to refresh, so just setting one of those properties (like dataField) to its current value whenever you set a formatter on it solves it.
Didn't test, but it looks like changing owner.invalidateDisplayList() to owner.invalidateList() in AdvancedDataGridColumn.set formatter should fix this bug.
Simple example showing the problem attached.