We haven't investigated the custom buttons recently as it hasn't been requested. From the quick research I just did, I can't find a good way to do custom buttons with the new Facebook API. We'll continue investigating though and let you know what we find out.
Better news for the remaining questions at least...
For shifting the button, I was able to move it around to what looked good to me with the following changes to your template.css file in the following location:
/templates/rt_mixxmag_j15/css/template.css
~line 58 in the #header-tools section, add:
padding: 12px 10px 0 0;
This will shift the button 12px down and 10 px to the left. However, when you do this, it will actually move the whole header bar lower. To 'correct', in the #horiz-menu div around line ~73, set the margin-top to 0px. Basically whatever you shift the button down by (12px) shift the whole menu up by the same amount (12px).
Regarding the logging out of Joomla vs Facebook, there's a setting in the JFBCLogin module to select whether you just log out of Joomla or out of both. Looking through our test plan, I just realize that this feature was not fully tested before the release. Please feel free to let us know your results, and if you run into issues, we'll get it fixed in the next release.
As for a ticket system, we don't have one. We use the forums exclusively as it (theoretically) lets people find answers on their own, though we obviously monitor and answer user's questions who have active subscriptions with a very high priority. If you have any feedback, comments, or suggestions on our system, we'd love to hear them.
Glad to hear 3.0 is working well for you otherwise though.. we put a ton of effort into it, and always worry a little with new 'big' releases no matter how much we test. Very happy to hear about the jReviews functionality too. We have big plans for tying into a lot of popular components in the future in some nifty ways.. first want to flesh out the minor bugs in the release candidate, but those are moving quick.
Finally, we'd love a review on the JED, they mean a lot to us and really help get more visibility for our extensions!