The only real plus about UBB is that UBB.X a scaled down version of UBB is available for free to those that use webhosting plans provided by UBB which start at $21 a month as of June 18, 2003.
Most of the forums I used to visit that used UBB have switched to Vbulletin including Gethighforums a popular webmaster message forum. As a user Vbulletin provides searching features that are much much faster than UBB. This coupled with Vbulletin's active community that constantly provides tweaks and custom hacks to the program make it the better software and its cheaper.
Only those with experience with UBB that have a preference for it should consider buying it instead of Vbulletin in my opinion.
UBB comes in three formats UBB.X which is free to
those who host with UBB, UBB Classic, and UBB Threads.
More about each of these forms of UBB can be viewed at
the the Official UBB Site..