Well, if you leave it in Creative mode, those that want to just build, can build, and those that want to mine for stuff the old-fashioned way, can do so.
When Mancraft II went up, I built my house and my runway (not the whole airport) out of my own stash of mined material. After I went through all my blocks (losing a nice amount of them to Furnaces, yay!), I decided to use the community blocks, because the part of Minecraft that is most fun for me is the crafting... The mining kinda got me butthurt with all the reappearing blocks and other bugs that get in the way of collecting and cooking.
So yeah, I think it'd be cool to let those want to build, build, and let those that want to mine, mine :D