I think Nether in multiplayer/multiplayer support for other dimensions is a great feature which had to be done, and maps in-game is also awesome. I just tried it on my server.
The server works horribly, though. There's a lot of lag, even after changing the chunk loading distance to 3! I can only see 32 to 64 meters in any direction! I like that you can make it 15 chunks, though, which is much bigger than what it was before, but with that the chunks are loading extremely slowly and the game is lagging terribly, making chests etc. impossible to use.
I really hope these bugs will be fixed soon. I got the 1.6_03 version, so I'll definitely check 1.6_04 out.