In a way Nepomuk in KDE is still a rather young and experimental project. We are still using a java storage backend since the Virtuoso one is not stable yet, we cannot track all file operations which can lead to orphaned meta data, applications so not use the theoretical full power of the framework, etc.
But I think this is OK. Nepomuk creates a new way of dealing with desktop data, even a new way of development (including ontologies). It is bound to take time, also because development it is not as fancy as for example Plasma and also a lot more complex. Thus, we should see the achievements so far positive. Apart from the existing frameworks and application integration there seems to be a trend towards semantic desktop ideas in general which is also an achievement of the Nepomuk project. There surely is a lot of potential.
On a more practical note there is one thing that has been missing for a long time: a starting point for developers wanting to help with Nepomuk. Sure, we have the tutorials which describe the system and how to use it. But no list of possible small or big projects to work on. Until now:
I already added a few todo items (mostly those I already discussed in previous blog posts) and ideas. I will continue to add items but I also urge you to add your own Nepomuk ideas.
(Why did I not use the KDE brainstorm forum? Because I need a dedicated Nepomuk page to keep an overview and track more complex tasks. The forum is a bit too scattered for my taste.)