For those who don't know yet, here's a bit of background information...
The plan for after Minecraft reached version 1.0 was to have a combined server instead of separate private and public servers. The existing maps from the private server and public server would be available in creative mode and survival mode respectively, along with a third new adventure map (also in survival mode, but with all the new adventure features).
When this plan was made, I personally had no idea about some of the aspects of creative mode such as infinite items. While I can see the benefits of this when working on big projects, it also renders factories obsolete. I understand that manufacturing is possibly a niche interest, but Pricetx told me to voice my concerns on here so here we are. When you get to the heart of the matter, it's not survival mode that we don't like per se, but enemy mobs like creepers and spiders. Pricetx has informed me that it's possible to have different difficulty settings between worlds, so I would like to suggest that instead of creative mode we have survival mode on peaceful with infinite health. That could also reopen the possibility of allowing items to be transported across worlds, since they would not be infinite.
And since I'm talking about manufacturing concerns, if somebody could figure out how to get buildcraft to work with bukkit that would be mighty splendid. I believe there are people working on this outside of the Jupiter community already. Spacetoad is adding pipe wiring to the latest beta which now makes it possible to automatically start and stop machines based on inventory levels (and many other conditions).