I realise this is not a forum for SIG Pro, but as it is used as a plugin for K2 and there is a separate image upload for the main image in K2, I think it is ok to post the request here.
IPTC metadata is used to add various bits of information to a picture. Things like caption, photographer, copyright, city, country, keywords etc.
I would like to see support for this and EXIF (metadata from the camera like exposure, camera model etc.) in K2 and SIG Pro. This avoids tedious double work as you anyway need to add this data if you are taking your picture archive serious.
It is definitely needed to be able to edit this data once the pictures are uploaded (same picture could be used in different situations), but the basic support should be there.
This is part of K2 moving from "publishing light" to "full publishing" (not talking about the number of articles!!!). We need the same attention to details regarding illustrations as we have for the text. Flickr already supports this and it would be nice to see K2 follow up.
This is yet another feature that would lift K2 above the rest and a serious feature for anyone considering opensource versus closed CMS.