Waf was originally created to ease the creation of KDE applications, but it has not worked so well in practice. The first versions of KDE 4 were terrible, and I think they discouraged anyone from using it ever again.

Fortunately, the version 4.9 has changed for the best, and it finally provides a pleasant development environment. At least, after the stability fixes (the plasma desktop does not crash anymore, the network manager just works), there are fewer annoyances than on other desktop environments. In particular, the focus stealing prevention policy helps to concentrate, and the apps do not pop-up password/keyring windows all the time anymore.

If Qt5 and KDE5 do not break the API too much, we should see more applications for KDE appearing over time.