Most of the time I have both Inkscape and GIMP opened. Vector gfx is being done with Inkscape and then imported into GIMP, and opposite direction.
I use Inkscape to finalize illustrations - typography, frames etc. Even if everything is set up (almost) perfectly there are unfortunately always a few pixels to tweak. Then I must switch to GIMP, retouch bitmap, reimport that illustration and do the resizing again (As noted in previous posts, Inkscape doesn't know exact printing size of imported graphics.). Another situation where I needed similar workaround was after reorganization of files. I run into the problem of having to correct all the links to graphics and then reloading the whole document to see the changes.
It would be very handy having option to update selected pixmap graphic from file.
Please don't be resent for throwing my working problems notes directly at this list. Afterall, these are all real life expiriences. :)
Cheers, Vlada