I agree with the suggestion that for the time being it's best to export from the print composer as a PDF and load this into Inkscape.
It's also worth bearing Scribus in mind. Get the map looking about right in the print composer and export it as a PDF. Then load the PDF into Adobe Reader and "print" it to a PostScript (.PS) file. This can be directly loaded into Scribus (don't create a new document, just import the file). In Scribus you can add text boxes, graphics boxes, symbols and labels, et cetera, and then export the finished product as a PDF.
I've been using this way of working for some time now and am pleased with the results I get. As a DTP package Scribus is very strong (and it's free, which is even better).