If anyone's interested, I wrote a (very small) vim plugin so that I can use an environment I'm already accustomed to. (It just automatically turns WikiWords into links)
It's probably got bugs.
I also came across this: http://tiddlywiki.com/
I like WikidPad because it's _fast_ in Edit mode (on-the-fly text formatting, like code highlighting), and it turns out to be a killer feature for me: without this speed I probably wouldn't be using it as much. With almost all other wikis I know, you need to switch back and forth between edit mode and preview mode, or they have a WYSIWYG editor mode (and I avoid that as much as possible -- just a programmer's obsession... I like to deal with the source).
I haven't used TiddlyWiki much, but I loved the concept when I first heard of it (self-modifying single file). It sure is a good way to get started fast.
My wiki has about 1,500 pages (a few MBs of text) and it's still very manageable. I use it for just about all notetaking purposes (you mention taking note about documentaries, it's one use case of mine; but the biggest is by far replacing bookmarks with free form text -- see link below).
The biggest advantage I see over text files is the graph structure you create by linking entries. I'll have a bunch of links at the top of each entry, and I'll add links whenever I feel it'll help me next time I try to find some piece of information.
About managing programming-related info: I have a bunch of code snippets in there too, along with more reference-like notes on concepts.
I've thought about using mind maps in the past, but I find it too limiting (I'd have to have a mind map + text notes in another system, and anyway I prefer something more text-y). But of course it's way better for visualization of the overall structure.
It's been a while, but a few years back I blogged about all this personal wikis idea (and wrote a post or two on using them for programming-related stuff), so if it may be useful: http://www.fsavard.com/flow/tag/wiki/