I'm pleased to announce that we've changed forum software from phpBB to vBulletin.
While phpBB has served us decently well over the last year, we've also had a number of issues with it. vBulletin has a better user feature set, and behind the scenes, a much better management experience. Importantly, it also has a very clean import path from phpBB, preserving all existing users and posts, the latter being especially critical as the thousands of existing posts are an invaluable resource.
All existing posts should have come across without issues. The one exception is that any post that included (such as in a code sample) the standard XML escape sequence of < which stands for '<' will in the imported version just have a '<'. There should be no cases or next to no cases of this though.
Note that any threads you were subscribed to previously (either because you explicitly subscribed to them, or because you checked the appropriate check-box when creating a thread) will need to be subscribed to again.
All user accounts should have imported successfully, for the most part. You do need to edit your profile to set your proper timezone, as this will not have transferred across successfully. This may be done in the "Edit Options" page of the User Control Panel. You may also need to edit any custom signature you have defined for yourself, if it has a quote in it, as " came across as \"editing, as " came across as \".
One other setting you will probably want to tweak in your user options is the choice of the editor to use when posting messages. By default this will be "Basic Editor", which is just a simple textbox, but you may want to change it to "Standard Editor", which adds some formatting controls, or "Enhanced Interface", which allows a full WYSIWYG interface using DHTML.
Be aware that as opposed to the old phpBB vehaviour, when displaying threads in a forum vBulletin defaults to only the last month's worth. Another value (e.g. all posts) may be easily specified via the dropdown at the bottom of the thread listing.
Expect the look and feel (theme) of the site to change over the next few weeks. Due to issues with phpBB it was considered important to make this switch now, before secondary aspects such as a final look and feel were fully done.
Working against the limitation that existing posts must not be lost, it will be our goal on an ongoing basis to continue to enhance the user experience on the forums. This means we will in the future further enhance the feature set with plugins to vBulletin, new versions of vBulletin, or even a move to other software where that makes sense and a clean conversion is possible.