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I've been doing a more primitive version of this for a while in KDE 3.5 by using two monitors and apps like Konqueror for tabbing harnesses.
Unfortunately, Konqueror 4.x is trash, but KDE 4.4 apparently introduces basic tiling and tabbing and you can get tiling on Windows with WinSplit Revolution. (Something I've begun to clone for GTK-centric X11 desktops under the name QuickTile)
Also, windows 7 introduces half-monitor tiling via window dragging, so they're not completely clueless.
...oh, and Fluxbox has had window tabbing for ages. (inspired by PWM, which introduced the idea in 2000) Edited 2010-04-25 01:08 UTC