Xara does the job smoothly and without putting the blur in a box. Can we expect the same behaviour in Inkscape?
By the way, note that Xara does not have blur - it only has _feathering_. In many situations they are interchangeable, but not always. Blur is more generic than feathering - that is, if you have blur, you can do feathering with it, but the reverse is not true.
-- bulia byak
Thank you for the explanation Bulia, I tried XARA and yes, the behaviour is quite different!! :) On the other side, the behaviour of Inkscape is still a little restrictive (10% box aroud the object is not very much) so it is not the most "comfortabe" tool for example to create a very diffused shadow... I attached 2 PNGs one created in Inkscape, the other one in xara.
The shadow created in Inkscape is a combination of gausian blur and circular transparency, and the problem is that the 10% box around the object is still visible... The shadow created in Xara is a combination of feather and circular transparency. Since there is no restricted 10% area, the shadow looks as it has to.
Thanks! Molumen