I think it actually depends on the site. Overall, I like Community better. But I find that when I go to a site like Opera's for the express purpose of looking in their forum, I quickly scan the links looking for the word forum. Although, they call it Community, so I have to then rescan the links for something that may lead me to their forum, I see Community, and then I say OK, it might be in there. It's a tad annoying. I don't know. It's just a thought.
I think people are gradually being exposed to "community" as a code word for "discussion forum" - quite a few major software sites and the like are using it for their "one word link" now. Despite the positive connotations of community, it may be a bit nebulous for some people.
Unfortunately, as "community" becomes more commonly used to describe forums, it will probably also lose its original positive overtones.