There will be a new version (ver. 0.47) of Inkscape out around june 15, 2009. There will be vast improvements in both functionality and stability over the current release.
Somebody is working on a ICC/CMYK workflow, and it will probably be available in the development version in a few month. Correct color management - seen away from CMYK separation and tagging SVG elements with ICC profiles - will probably be available in ver. 0.47. At the moment, the limitation in CMYK separation can be worked around by using modified ICC printer profiles.
A new spray tool has been developed, but it has not been finished in time to come into the new release. It will be included in the development version soon after the new release.
Else, I think the worst limitation in Inkscape at the moment, is the slow rendering if you work on designs with more then 100.000 vectors/points.
The calligraphic tool, the filters, clone and tile, live path edit and the Python scripting in Inkscape are almost unsurpassable, but I don't know the other programs sufficiently to compare.