Have used wikis since 1996, starting with Ward's original wiki.
Have used TWiki since, oh, 1997 or 1998(?)
Have evangelized - used, installed, promoted - wikis, mainly TWiki, but also MoinMoin , ZWiki, UseModWiki - at the University of Wisconsin, Intel, AMD, Intel ...
I remain a wiki fan, although seniors at two different companies and one university have told me that I have been wasting my time. So far, about 25% of the projects or groups I have evangelized wiki (usually TWiki) to have picked up on it; in the others, wiki usage peetered out after the prime mover (me, or WayneScott) moved away.
Latest (2006): I'm back at Intel, and I am hopeful that wikis have finally reached critical mass
Intel IT has just started wiki and blog sites
TWiki now semi-officially supported by Engineering Computing Support
Others, and myself, revived Wayne Scott's original twiki at Intel, then proceeded to create our own installations
Upwards of a dozen wikis at Intel, that I know about.