A little less than two months ago, we improperly deprecated the Plugin API for Cordova Plugins. The reason for this was to move from the old architecture to the new one. However, it seems that once again that people ran into problems with this because we didn't publish the changes on the blog, and only put them on our deprecation page in the wiki.
Because this change caught a lot of people by surprise, we're going to re-introduce Plugin.java back for 2.8.1 and 2.9.0. We will not support these plugins in the upcoming 3.0 release, and we expect that plugin maintainers will update their plugins and conform to the new plugin spec that we are working on if they want users to actually use their plugins with new tools that are appearing in new releases. Currently there are way too many plugins that don't work with the current version of Cordova. There will be more updates about the new updates to Cordova, but for those people who are unwilling or are unable to write the Java code required to upgrade plugins, we put it back. However, this is temporary and your old plugins WILL NOT WORK with Cordova 3.0.
Furthermore, the 2.9.0 release will be a long-lived release and will be the last release of 2.x Cordova. All versions of Cordova after 2.9 will have their plugins removed, and will depend on the new plugman tool. This is done so that apps that don't need things like GPS or Accelerometer don't have that extra code kicking around.
Finally, there is one other change in 2.8.1, which is the update script. The update script was created from the create script, and contained a major bug where it deleted projects that made it not suitable to be used by anyone, and unfortunately we didn't catch it until now. It's now been fixed and the update script should work, but I recommend reading the scripts before using them. Fortunately, it only affected Linux and MacOS X users, and Windows is unaffected by this change.
Cordova-Android 2.8.1 will be included in the 2.8 download package from phonegap.com, so I highly recommend downloading and updating to the latest version from 2.8.0 and lower.