Observed behaviour:
In FX 2.2, a ComboBox's selected item is rendered through its toString() method.

Expected behaviour:
The selected item should be rendered through the ComboBox's CellFactory.

This is a regression from the 2.1 GA release. The attached code illustrates the issue.
This issue is probably related to RT-21933, where the CellFactory appears not to be used to render the "null"-item.