Better late than never... Stephen Silver has created a generic Python module for running external convertors for import which is supposed to work on any platform (before, we had shell scripts which were troublesome on Windows). It is used for CDR input with Uniconverter, and I have used it for EPS and PS input via Ghostscript. It uses PDF as intermediate format and imports it using our Poppler PDF importer as a helper extension. As a free bonus, we get the same PDF import options dialog, which makes sense for choosing pages when a PS file had multiple pages.
There's only one prerequisite: install Ghostscript and make sure ps2pdf is in your path. The pstoedit, sketch, etc. are no longer needed.
Please test and let me know if there are any problems.