I have not posted anything about the progress of my researches into Eclipse and Maven integration for a while. That's because for a long time, we didn't get significantly further along in our research. But just recently we've started making significant progress again.
A very important lesson was that the pde-maven-plugin is really not worth persevering with - at least in our situation. We decided that we wanted to build every Eclipse plug-in and every Eclipse feature using its own POM, so that we could for example generate code coverage reports for each component individually and also configuration-manage them at that level of granularity. It turned out to be not all that difficult to invoke the PDE headless build for these circumstances from Maven using about two dozen lines of Ant script.
After nine months of Eclipse 3.3, the pde-maven-plugin has still not been officially updated to handle the changes from Eclipse 3.2 (we had to use the Alpha 2 snapshot version downloaded from Codehaus) and so we're concerned that we might have similar upward compatibility problems when Eclipse 3.4 comes out in a few months.
When it's all been finalised, I hope to publish a longer explanation of how our build system works here. Don't hold your breath though; at the moment we still have to solve a few issues - for example, we need to figure out how to produce the source plug-ins alongside the executable ones.