Well, this one took me quite a while, but it's perfect
Distro: Arch GNU/Linux
DE: KDE 4.7 RC1
Plasma Theme: Glassified
Widget Style: QtCurve
I recommend it to be used with 'plasma-widget-menubar' or 'bespin's xbar' or 'oxygen-appmenu', the menubar background perfectly matches with the window background gradient though.
System Settings> Workspace Appearance> Window Decoration> Oxygen> Configure Decoration> Fine Tuning> Background Style = Solid Color
Oxygen (the windeco) has been improved in KDE 4.7 and got some new intresting features
Download (save) the image for a sharper preview, it's kind of blurry here on dA.