Why does Ubuntu 14.04 stick with (old) Eclipse 3.8 when 4.3 is out?

Eclipse Juno was released 2012-06-27. On 2012-07-17 a bug concerning the responsiveness of the UI was reported. Four months later, around 2012-11-14 the first patch was released to the official update-site.

Many users, however, completely missed the release of the patches. I assume the information drowned in the FUD, and other more important news, that was spread around that time. At the end of 2012 I posted an answer on SO. Apparently I was not the only one for whom the patch fixed this performance issue. On 2013-02-22 Eclipse 4.2.2 was released, which contained the same patch, yet I kept receiving upvotes for my answer on SO until June.

Probably the only known fact among developers is that Eclipse had serious performance issues at some point. However, the knowledge about scope, magnitude and duration of these issues seems to me like a series of common misconceptions. There was a four months period during which it was a good idea for many Eclipse users to stick with the 3.8 branch. I say "many" because I worked with 4.2.0 and 4.2.1 and it was O.K. for me. Subjectively, switching tabs was about two times slower and the IDE froze maybe once a day for a couple of seconds. For colleagues of mine the problem was much more severe. I assume it depended on your setup and on your workflow, however, I never felt like investigating further because I knew the platform developers were working on the issues, and there was a good fallback, using 3.8.

One year and three Eclpse releases later these serious performance issues are still fixed. Of course, this doesn't mean that there are no more performance issues. As of now I find 1979 reports in the Eclipse bugzilla with the keyword "performance". This doesn't mean that Eclipse is very buggy, but only that it is very well documented and open. Whether or not you are affected by any of these issues, again, depends on the setup, the plug-ins you are using and your workflow. I am a Java, plug-in and EMF developer. I work with medium to big work spaces (~1M LoC), and Eclipse 4.3.1 is fast enough. The 3.8 release is not an option for me because as Eric said, it won't receive all of the important updates. People will still continue using it in the future. Many of them will also continue using Internet Explorer 5.5. If you try the 4.x branch and notice any performance issues, please report them, but be specific about your setup.

From the official Wiki page:

Several major performance defects have been addressed in Juno SR2 (4.2.2). Community members have confirmed that these fixes substantially address the performance problems with editor and view opening, closing, and switching. These fixes are widely available in Juno Service Release 2 (February 2013). All defects are also resolved in the Kepler (June 2013) release stream.

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Your statement "3.8 release was specifically released as a faster and more stable alternative to 4.2" is clearly incorrect; 3.x has gone into its 'end of life' maintenance and was most certainly not released as an alternative to 4.x.

While folks are welcome to continue to use the 3.x stream if it suits their needs please recognize that as the various projects move forward there will be significant divergence in the features available between the two versions...