OpenMoko Freerunner¹ is ARM based and it launches the Qtopia / QtE, GTK and E17 UI stacks. All of them are also supported on x86. The GTK is based on Cairo, and I have heard (not sure) that it uses a lot of floating point calculations, so ARM with GTK may not be very fast.
¹ http://wiki.openmoko.org/wiki/Neo_FreeRunner
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