Ian pointed me to this posting by James Avery, who seems to really like ScrewTurn wiki, an open-source, .NET-based wiki engine just like FlexWiki. But James' statement
I have been using FlexWiki for sometime and I have to say that Screwturn really blows it away. It has built in security, one-click backup, its extremely customizable, and much more.
sort of caught my eye, as you might imagine. :)
Contrary to what seems to be the unfortunately frequent open-source practice, I'm not interested trashtalking ScrewTurn wiki. In my ideal world, ScrewTurn would do everything that FlexWiki does, plus more, and there'd be a syntax converter. Then I could switch to ScrewTurn wiki and spend my limited free time making it (or something else) better. Since that doesn't seem to be the case (it looks like they both have features the other lacks), I guess I'm going to stick with FlexWiki for now. :)
At any rate, if you're in the market for a .NET-based wiki, I highly recommend you check out ScrewTurn. I haven't installed it yet, but I've skimmed the docs, and it sure looks like they've got a solid project. It looks like for now the choice between FlexWiki and ScrewTurn depends on your particular requirements and preferences, so it's good to know about the options.
And to any ScrewTurn devs that read this - if there's anything FlexWiki can do to help, or if you have suggestions about what we can do better (there's lots), or if you can think of interesting ways to work together, just let us know.