The wiki strikes me as similar to GitHubs wiki / pages stuff (which seems obvious enough). Which I appreciate the features it offers (markdown, git, etc), I don't feel like the majority of people using Confluence would, and the feature set is indeed fairly different. Not bad, and I would certainly use it, but I'm not sure it's a replacement for Confluence users.

The issue board on the other hand seems a lot closer to a "replacement" for Jira. The tag based concept reminds me (again) of a Github 3rd party tool, but it's nice that it's built in. Again, less feature-rich compared to Jira, but in this case, not necessarily a bad thing. Jira can be overboard for most workflows. I might have to give that a try.