I downloaded and installed build 500, but it seems that there is a problem with the plugins.
First of all, the "Plugins..." menu item seems to be gone. Weird :) Then, some plugins (see http://www.intellij.net/forums/thread.jspa?threadID=268269) cause a "Method not found"-Exception (I posted an issue: http://www.jetbrains.net/jira/browse/RSRP-45382). In 3.0.1, plug ins worked nicely.
Are there any important (intentional or unintentional) changes concerning plug-ins in build 500?