The new beta version  of the Eclipse Plugin for Scala has taken a big leap forward in robustness, reliability and responsiveness. Over the past few years Miles Sabin together with other dedicated contibutors like David Bernard, Matt Russel, and Mirko Stocker have steadily improved the quality and features of the IDE and by doing that have rendered a great service to the Scala community. In order to make a break through in performance and reliability it was seen that the fundamental way in which the plugin worked with the Scala compiler must be rethought. Compiler changes were needed and the plugin design changed to effectively use the compiler's new capabilities.
Miles has handed over the baton to the Scala Solutions team of Martin Odersky, Iulian Dragos and Eugene Vigdorchik who will lead the next development phase of the plugin. After about two person-years of hard work including contributions from Donna Malayeri and Hubert Polciniczak from the Scala team at EPFL the compiler interface has been completely revamped and now delivers better responsiveness and reliability. Actions such as hyperlinking, completion and real-time type checking now work quickly and reliably even on very large projects. The team believes you will find this release a firm foundation on which you will see the IDE grow to include all new features we expect of a modern IDE.
The Eclipse Scala plugin is an open source project so new contributors are welcome. The software is freely available for download from the Scala-IDE site  and works with version 2.9.0-RC1 of Scala.
If you are an Eclipse user then you may enjoy giving the new Eclipse Scala IDE a try.