I just committed a new blurring code which works much faster by using
subsampling and linear interpolation. Of course this is somewhat at
the expense of quality, but I think the quality is still acceptable,
yet now it renders with tolerable speed, even at high zooms, which
makes blur actually usable. (Check it out in the svg-filters branch!)
I think eventually we'll need to provide a user option to set the
level of subsampling to accommodate different hardware performance, as
well as to make sure it's turned off during bitmap export, for maximum
quality of the exported image.
Inkscape. Draw Freely.