You could probably achieve a similar effect using some combination of objects with blur and transparency but it probably wouldn't be very easy or intuitive.
On an unrelated note, I've finally started using node sculpting in Inkscape and I must say that it totally rocks, especially with pressure sensitivity. If Inkscape can achieve some performance improvements via Cairo etc., I may need to reconsider my earlier statements about Xtreme's superiority for doing freehand drawings.
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