Has anybody found examples of using FXG files in real world applications?
For what it's worth, Adobe Illustrator saves in FXG format.
Other Adobe applications supporting FXG include Fireworks, Flash, Illustrator, Photoshop and Flash Catalyst.
Microsoft Expression Blend allows importing FXG 2.0.
On the open-source side, SpecFXGExport enhances Inkscape to export FXG files.
Additionally, this might be of interest: FXG Editor for Flex.