I heard about PHP-Nuke before and it looked really neat, so I was interested to hear about the security bug in v 2.5 mentioned earlier. Funny, when I checked that link, I read that v 3.0 also has a security bug:
http://virtue.wox.org/~virtue/articl...readed&order=0
PHP-Nuke seems to be a promising product but it's a shame that it's not handled professionally (i.e. not a lot of info on the website, those security bugs, administration of project on sourceforge.net not handled very well, people behind it seem to know little English).
I might give it a try anyway, but if it cost $200 and it was as professionally handled as vBulletin (or even integrated), I would be ecstatic and buy it straightaway (hint, hint) - like I bought vBulletin.
P.S. Does vBulletin also have any security bugs?