I have 2.6.4, and I don't have that in my Layers menu. Have you installed plugins or scripts? Those can modify your menu items.
Anyhow, are these layer effects destructive? They're doing some sort of new system for GIMP that has nondestructive layer effects and stuff like that, and there's a GUI redesign project going on too! So, exciting days ahead. Too bad gimp.org doesn't load for me at the mo.