So I finally bought the box set and watched the first few episodes last weekend. So far, I can't really say that it was worth the money. The picture quality seems to be only marginally better than on the DVDs.
One episodes (I think it was "Unexpected") even had a music cue slightly cut during a transition from one scene to the other, while it was perfectly fine on the DVD. That's annoying! Good thing I still have my DVD box sets!