This may or may not help you crow, but I use CB1.1, Juga, PHPBB3, AEC, & Freeway all together pretty well, almost without a glitch (unless I caused them). The only thing is, there is no support for full PHPBB3 integration at this time. If you look on Joomla.com's extensions directory I have seen some PHPBB3 connectors that make modules in Joomla to display newest & also recent user posts. But, user authentication integration, whilst still in its "beta" stages, is best achieved using the bridge "rockbridge RC3" from rocketwerx.com (I am not affiliated, I am just a customer).
I use AEC for my users to choose either a "free" or "paid"subscription as part of the registration process.
I use Juga to create additional user groups & set access permissions to content/components/modules/plugins based on those groups. AEC & Juga work nicely together (which is good info to have seeing as how if your are new to Joomla, like I "was" 4 months ago from there to here can be a wee bit frustratin...but well learned lesson) anywho...tokin a bit to much reef and ramblin here
Community Builder integrates nicely in the whole process and both AEC & JUGA(costs $29.99) have integrations for it that actually work...
And lastly, Freeway is an E-Commerce solution which I am trying to use instead of Virtuemart...I am having trouble getting the users between Joomla and it to sync...but I do have the "other" to fall back on and isn't all that bad if you are forced to use it...+ user integration works like a charm.
...well hope this helped if you have any more ?s feel free...I'm attached to my computer 20, no 24, no 38, no 2000...aw hell I've lost track of time again( you get the point)