AlterBrains

Okay so this is the situation with my site. I had Joomla 1.5 with JFusion and phpBB3, and I had users to register with JFusion to Joomla, and then the user was able to have the acct on the Forum also.

Here's my question, if I delete the whole Joomla 1.5 from my site, leaving the Forum intact, and install Joomla 3.0 with Bridge. Will the option to Migrate users from the forum onto Joomla 3.0 work with Bridge? Without any problems to their passwords or phpbb3 information?

All phpBB information will be preserved and you will be able to copy users from phpBB to Joomla.
But note that phpBB and Joomla have different password storage methods, so direct login in Joomla with phpBB password will be impossible without a bridge.

With bridge installed it will also check password from phpBB and if match - update Joomla password to correct hash. Next this user will be able to login in Joomla with old password even without bridge.

So basically no issues will occur.