How to hard reboot out of Scala/Eclipse re-build hell

I find it hard to believe that I am the only person who is occasionally stuck in eclipse workspace-rebuild hell. The workspace simply does not clean or rebuild as it is supposed to, or takes an extraordinarily long time. I understand the reasons include the complex type inference and the fact that Eclipse doesn't really take not of updates cleanly. Anyway:

1. Blow away all your code (just for fun, mostly). 
2. If you weren't using source control, what the hell is wrong with you?
3. Delete all your packages in Eclipse - (moderately satisfying)
4. Blow away project properties directory called project  (not sure if this is strictly necessary but it feels terrific)
5. Pull a clean copy of your code and everyone else's
6. Start over. Run  ./sbt nars eclipse    - or whatever. File->Import->General->Existing Projects into Workspace

I find this usually does the trick, but would appreciate thoughts from an expert on why it should be this hard. Thanks to Dan Glaser by the way.