I have connected my phpbb3 (with more than 1k users) to newly re-design Joomla site. And it works just fantastic for me.
It works without any core hacks, it is important for me, But I am still looking forward for such a Jfusion version which will not make any permanent changes to my Joomla user table.
We also expect to get two-way user sync functionality in coming versions.
Any way! It is very nice utility to integrate a high powered, fully scalable, and highly customizable bulletin board package Phpbb with leading CMS Joomla.
Full marks to you. You deserve it.