As for the Eclipse UI Guidelines, it's good to revisit that, but I think they only address a limited portion of the UI issues: they help maintain consistency across Eclipse IDEs/plugins.
However, if we want to do something more fundamental, like change or redesign certain aspects of the Eclipse workbench UX , we can't do it with just the UI Guidelines. And without a "product manager" like Doug described it, it would be hard to get consensus on some of those changes. (not to mention developers to work on them)
For example, I think the workbench would work better with perspectives used less. Maybe reduced to just a General perspective and Debug, as was mentioned before. Or even further, to just one perspective, but that would require smarter view management (debug views or view-folders popping in and out according to debug sessions, etc.). Management of launch configurations also could use an overhaul. I'd like the see the name of the currently active launch configuration in the toolbar, like IJ, or CDT's LaunchBar. Having transient launch configurations is also a good idea. Another thing I liked with IJ's workbench was implicit auto-save (that's more than just auto-save).