What we're doing: We're writing vanilla joomla (and JomSocial) plugins trying to push Joomla and JomSocial data (fields and Group memberships) to a 3rd party system.

JomSocial version: 3.2.0.5
Joomla version: 3.3.0
php version: 5.4.4

1) "Resolved" bug (yet still quite problematic for others): Try the following plg_user_something plguin:
onUserBeforeSave($user, $isnew, $data){$cUser = CFactory::getUser($user)}
This will immediatelly throw the system in a recursion. CFactory::getUser() calls init() on the new entries in the CUser object cache, which in turn calls save(), and then we loop back to onUserBeforeSave.
This is just an example, the amount of recursion is immense (I've seen stack traces 50 levels deep when I use the JomSocial models/users in plugins). We avoid this by essentially never using any CUser or community models (they instantiate CUsers too), and instead hitting the DB (therefore loosing all our forward compatibility). Also, in the aforementioned example, JomSocial ends up breaking the front-end registrations (but the recursion is so deep, I'd hate to do an entire analysis of what's going on).

2) Also "resolved" bug: All azrul.ajax calls appear to be made in an improper fashion. Instead of going to a controller named something.json.php they go to something.php (so the implied format=html kicks in). This produces a JDocumentHtml, which may include html from other sources (like data injected from the Joomla --or others-- debug plugin). We fixed this one by essentially checking the JInput against option values of "com_community" and "community".

3) The real unresolved bugs: We need to know when a user enters or leaves a group (be it from the front or back-end) so we can inform our external data storage (a CRM).
Hooking on the JomSocial group events:
* The back-end does not fire the onGroupJoin, onGroupJoinApproved and onGroupLeave events at all (adding users to groups from the back-end Monitor tab by clicking on the yellow 'Assign to Group' buttons).
* If a user applies to be a member of a private group through the front-end, in the back-end (through the yellow 'assign to group' button) he is listed as a member of that group in the pop-up window.
* On the front-end, the onGroupLeave is not thrown at all when a user leaves a public group (did not test with private ones). Searching through the sources for the 'onGroupLeave' string, the only file with a hit is /components/com_community/controllers/notification.php at line 845 inside the 'ajaxGroupRejectRequest' function with the comment 'Ajax function to decline Private Group Request'. This does not match the event name nor description (and explains the lack of event firing).
* (fixed) The front-end appears to throw the onGroupJoin event upon a users attempt to join/apply to a private group (clicking on the blue 'Join Group' button while viewing the private group in the frohnt-end). This is done via the components/com_community/controllers/groups.php line 2163: $this->triggerGroupEvents('onGroupJoin', $group, $my->id); Again, the documentation and event name contradict this usage. We resorted to using a CTableGroup, loading it to the $group->id fed to the event and then checking against it's ->isMember($memberid) check.
There may be more issues here, we did not test thoroughly as about half of the already functionality is not present.

We may be incorrect in our comments and approaches. Please do tell us if we're doing something wrong or missing something.

Hi, Dom.

I assign developer to this thread.

Any update from the developer?

Thanks,
Dom

Hi, Dom.

He's assigned to the thread so he'll reply as soon as he can.
Assigning thread to developer means that it took a while when response will be posted as they work mostly on "hard cases".

Hi Dom,

I am closing this post as i notice they are answering you in the Jomsocial extension group