Well, so far Smack and Spark are both on Github, and the experience has been pretty easy (at least now most kinks have been ironed out).
Jira continues to be the issue tracker for the projects at the moment. Jira offers a lot more features for an issue tracker than Github issues does, however that may or may not be needed. Sometimes simplicity is nice. I think it may be a large effort to get all current Jira tickets into Github Issues... but Github Issues offers a lot more integration when using Github as a repo... I've no preference personally.
I believe there is a one-way communication between github to jira (or is it the other way around?). Fisheye, I do not know, however, Fisheye is redundant of much of the Github UI. Fisheye isn't suggested by Altassian to be used with their Stash product or BitBucket product, and both emulate Github, so it's doubtful Fisheye will add anything useful for projects on Github.
Bamboo works fine with Github, right now I think Daryl set it to poll Github every 5 minutes for new commits, and if any are found, it builds the project.
Project leads will need to review pull requests (unless delegated to a trusted contributor) and apply changes to the Master branch of the repo (github can email you notifications when a new pull request is opened, and most pull requests can be auto-merged with a 1-click button). When changes are applied to the Master branch, Bamboo will notice, and will build it.
I don't know about the github wiki. I've not used it much... so i don't know if it offers anything better. If anything, I don't think we're going to switch away from using the Jive SBS for forums and the website... so maybe the wiki-ish stuff should stay here as well. I think Matt (or maybe it was Benjamin 
) has said at somepoint Jive was planning to upgrade us to the latest and greatest Jive SBS 