The task manager for the KDE Plasma desktop is much-improved in the upcoming KDE 4.11
release with some parts of it being rewritten from scratch to address longstanding issues while other improvements are making it ready for QML.
There's a lengthy blog post at blogs.kde.org
that cover the KDE 4.11 Task Manager improvements.
Written by Eike Hein, the post covers the better layout of the task manager in the new applet, consistent interactions with the new task manager, visual fixes and polishing, better integration with the rest of the KDE Workspace, improved configuration handling, and better performance. This QML-powered Task Manager is what will also be found in KDE Plasma 2.