I've spent the last few months on the behind-the-scenes architecture of KStars. Since the port to KDE4 was going to be a major overhaul for us anyway, we decided to simultaneously do a major refactoring of how the data catalogs are represented in KStars. We're now using a hierarchical Composite/Component model, and it's working well.
Once that was nailed down, I began the dull drudgework of porting to KDE4. It was mostly search-and-replace, followed by bug hunting. Class by class, I replaced QPtrLists with QLists, for(Iterator)'s with foreach()'s, and QPoints with QPointFs (to name a few).
All of that effort was in service of a dream: of seeing, for the first time, my beloved KStars rendered in full antialiased glory. Ladies and gentlemen, I give you: KStars under KDE4:
First, KStars under KDE4. Then, the same view, with KStars under KDE3.x
Here also is a detail showing the antialiasing:
KStars still needs a LOT of work before it's usable under KDE4, but it's really nice to at least see it in action again.