Trueg is the KDE-Nepomuk dude, and has been running a few cool blogs, for example about Nepomuk Virtual Folders - The Next Level, We Don't Search... and Fetch, Nepomuk, fetch!
Tagging is the future. Overcoming typos in tags, synonyms is a conflicting feature, but does not limit the wide applicability of being able to tie information together. Now, Nepomuk is a bit strict on the type of metadata allowed, which is why Strigi has a super ontology (as in super set), to which we can add chemistry bits.
I have yet to install KDE 4.1, assuming that a good deal of truegs work found its way into that. At least, the virtual folders bit, I hope. But just imagine tying together PDFs, PDB entries, etc, I have on my desktop, all belonging to a diabetes, by just typing this URL: nepomuksearch:/diabetes.
On a different note, this tagging if available in Kmail would provide a powerful approach to organize the processing of my inbox; I can tag emails with todo, toreply, toread, toarchive, ...
Oh, and let me squeeze in this statement too (sorry, jriddel) : Kubuntu 8.04 has required me to tweak to work around bugs than any other previous Kubuntu release. Things tend to be encountered by others earlier, so that Googling generally helps sufficiently. But missing dependencies is a bit ugly (sorry, forgot which program it was, so can't link to the bug report). And, still am a happy Kubuntu user!