kwin-tiling now features dynamic layout switching per desktop. Use Meta+PgUp for Columns and Meta+PgDn for Spiral. Watch the windows change their place on the fly!
A few bugs in both the layouts are also fixed. Overall kwin-tiling is pretty stable for now, so give it a whirl and notify me of any bugs you can find.
What it still lacks is Xinerama awareness, but otherwise its virtually feature complete for the first release.
Unfortunately since college has begun I've been able to work on Kwin for only a few hours a week, so progress is a bit slow.
But the good news is that since GSoC is over, we should start seeing loads of new features being integrated into trunk/ to play around with.