Google always seems to return the old site as a the top search result. Since that's the case, should you redirect traffic, or maybe provide a link from the old site's mainpage to the new one.
Indeed.
When the forums were moved over to the new address and we started with some of the issues of essentially having the code running in two places, as separate entities, simultaneously, I mentioned that the old site should be taken down to skip running into more glitches in the proverbial matrix. But that rather than pull the rug out from under the community the
http://www.nogoblinsallowed.com address should still be something, even if that something is simply a white page that says "In preparation for the launch of the front page our forums have moved here: Link"
This would keep all the links that people have sewn across the net coming back to at least a page that links to the forums, and would still have all of the cached information that's stored at Google not go to waste, as well as making the launch of the front page a much smoother process.