One of the features that I was very eagerly expecting in 3.5 M6 is PDE's Custom Attribute. As of now, the Manifest editor has very limited ways of editing an attribute in the plug-in. It could be either String/boolean/Java/Resource/Id. What if PDE provides an extension point and you could plug in your own controls in the editor? Well thats exactly the Custom Attribute feature that I'm talking about. I've been playing it with for a while, and its awesome. The possibilities are really endless and here are some samples:
Pick your favourite color:
Select the SWT Platforms you support:
Choose an icon from your plug-in or shared images:
Or the best I've seen - define the location URI for a menu/toolbar contribution:
You can even provide auto complete in the text editor tab:
This feature is not just cool one, but also a useful one and will boost productivity. Its very unfortunate that it slipped this milestone (M6) due to work load. Its even unfortunate that beyond M6 no API/extension point can be added. What this means, we have to wait till 3.6 (released in 2010) to get this feature. Or somehow convince *everyone* that its should be pushed into 3.5 itself. Martin says "that is not impossible", and the way is: "to go through the process (e-mail and public discussion on eclipse-pmc list)". As everyone is busy with EclipseCon, I think that this process would start after EclipseCon.
Meanwhile, if you like this feature and want it in 3.5 itself, why don't you vote for this bug? I'm sure community's voice will be heard. If this gets into next milestone, I'll promise that I'll write a tip on how to use this extension point :-)