Now KDE 4.10 has been released, the Smoother plasma theme I'm working on will be ready for KDE 4.10. There is nothing major but I'm just making sure it will offer some of the changes in 4.10, specifically new widget handle icons, adapted thin scrollbar design and some other bits that have changed.
It's nice to work on themes that don't break in every release, KDE have done a great job in preserving legacy for theme makers throughout the 4 series and extending customisation, UI options for the users. KDE4 isn't a one size fits all design, so never does it force a hard coded desktop design that's half for PC's and half for other devices(i.e like GNOME3, Windows 8, Unity does), it gives you a desktop the way you want it. KDE also made good decisions at the start of KDE4 with Kwin and desktop compositing, you don't need a separate desktop if you don't have 3D acceleration, in fact KDE4 can use Xrender software acceleration, which gives you some of the features of 3D acceleration(like translucency) and you can switch to 2D mode by just Alt, Shift, F12. KDE4 does some other nice tricks, which really are transparent to the user(pun intended) but the technology behind it is so simple, like translucent widgets without desktop compositing running at all. This is done because the widgets are graphics(SVGs) not windows or top level windows like the panel, which require compositing done by kwin for translucency. Compiz and Mutter(GNOME 3 Window manager) don't work like this, they have to drop back to another window manager like metacity for 2D mode and it's simply not a good experience to have to login to another session just for 2D or 3D mode or if your driver fails.
It wasn't all a smooth ride for KDE4 of course but their design decisions have paid off nicely, especially in regard to kwin and nicely integrates the desktop effects into KDE4 with a UI in the system settings.