Last week a mail came through the NEPOMUK mailinglist, positive feedback. I am happy to copy it here - because it programmers like the KDE guys appreciate positive feedback, usually only angry people bother writing mails:
I've been playing around with Nepomuk and his cousins since the early
days. Posted to forums about setting up virtuoso when it was
introduced. I just wanted to make everything KDE to work properly; it
wasn't like there was an major, urgent need for search.

Today I went looking for a file using search in Dolphin. Things have
come a long way with search. Fast and accurate. I found what I was
looking for with ease.

Thank you all so much for what you've contributed.

(p.s.: I don't copy the name of the submitter, as I don't know if he would appreciate it. If you are curious, check the mail archives)