If you've been waiting for the stable release, don't hesistate any longer!
For those who are not familiar with the project: HgEclipse is a Mercurial plugin for the Eclipse IDE, geared towards enterprise use.
AFAIK it is the best performant and most feature rich Mercurial plugin for Eclipse.
Change highlights from 1.5.0RC1:
* History View: easier navigation with "open" and "compare", faster graph view
* Merge View: 3-way merge to resolve conflicts, more convenient context menus
* Lots of bugs fixed