MyWorlds is out. Basic portal functionality is b0rked. We ended up with one-way nether portals.

Back to Multiverse. I've removed Multiverse-Portals and replaced that with Simple Portals.

Things now work as expected and we can create custom portals like the one at spawn that goes to the IslandWorld.

The custom portals also allow entities to travel through them. Haven't tested with regular Nether portals yet. But either way we can create multi-dimensional farms now or gather mobs from one dimension and move them to another.