I don't like spawning items that people can get / make on their own. Go make your own:
- glowstone
- glass
- obsidian
- lava
- bookcases

I don't mind spawning items that keep people enjoying the game:
- tools
- steaks, chops, bread
- goofy shit (cake, cookies, and sticky pistons)
- redstone
- paintings

This portal thing was driving me insane. Because you need a stronghold, and because of the 1.8 architecture, there's only 1 for the entire map ... which might or might not have the air gate pending on when someone ran over that part of the map ... I gave up. "The End" is crazy looking, but pointless too. Nifty there's another world, but TNT and diamond picks barely get the job done.