As requested on Twitter, and potentially related to Team -> Synchronize should be allowed when selecting multiple projects.
HgEclipse can currently sync a single project to a single repository, and according to the comments on the other ticket it can also sync multiple projects in one go. Currently this only works against a single repository, as projects from other repos get a message about the repo being unrelated to the project.
Ideally for usability the HgEclipse plugin would allow a sync to include projects from many repositories, as this does not seem an unusual way of working and is already supported by the built-in CVS and both of the main SVN plugins.
The best solution (IMO) would be to combine all uncommitted changes in to a single "uncommitted" group and commit to the appropriate repo based on project if multiple files are committed at once, and to have all of the push and pull changes grouped under a single push and a single pull group, using additional annotations on the name to identify the repo. This is basically the way that Subversive works and makes it easy to skim and pull down or push everything, if necessary.