Just a quick update this time, I haven't finished anything especially noteworthy lately, so I haven't blogged about them either. The bugs mentioned in my last post have been ironed out, as well as some others. I did make the blur slider such that it didn't create a full new filter every time it was invoked, but as I committed that change, it became apparent that Nicholas Bishop had been working on the same code for his GSoC project on filter effects UI. So, that my code was obsoleted in a matter of hours. Re-implementing it, so it can work with this new blur & blending mode UI, could be useful though.
My plans now are to implement new filter primitives. My original plan states feMerge and feComposite, but as turbulence and lighting effects were considered really useful, when I discussed this on Inkscape Jabber channel, I might implement them first.