I have to echo some of what Simon Schäfer said. The (subjective) code quality of JDT is poor in many cases, several abstractions not very well done. (it's a bit too much to go into detail on what exactly)
I also echo that it is unfortunate that a project that tries to refactor common IDE infrastructure never successfully came to life. TBH, before LangEclipseIDE there was DLTK - Dynamic Languages Toolkit, which I consider to be the first serious attempt at this. DLTK is also based on cloned JDT code, and despite being named for "dynamic" languages, 80-90% of the common IDE infrastructure it provides applies equally well to any language, dynamic or not. That's why DDT used DLTK for most of its life span. But DLTK was short-lived and quickly lost backing, and this before they even had a chance to cleanup/refactor some of JDT's cloned code, so DLTK is left in a very poor state too.
So, despite the idea of a common IDE infrastructure project being discussed and talked about many, many times over, it never came to fruition. However, I am not surprised, or even disappointed that this is the case. This is because I understand that, Eclipse being open-source and having the corporate backers it has, such a big project would never materialize unless there was a corporate/business interest behind it. And there never was. IBM - for many years and probably still the main backer of JDT - does not really have any significant business interest in refactoring JDT out to make it easier for new languages IDE to be made (non JVM languages at least). It has some business interest in allowing the IDE to be extensible so that new *Java-related tools* could be built on top of JDT. Like Java EE tools, Java code analysis tools, etc.. And indeed there are lots of those.
But if there is no business interest in a common IDE infrastructure project, I can't really expect it to happen, from that team at least.
The same thing happened with CDT. CDT copied JDT's code, and of course, could theoretically also have refactored that into a common IDE infrastructure project. But realistically, it would also not serve the business interests of whatever companies where backing CDT, so it didn't happen. (well, yes, it might have some minor benefits, but not enough to justify the *cost*)
Part II:
The thing that actually disappoints in the state of Eclipse, is shortcomings within the Platform code itself, core and UI. Not as in major new functionality I would want, but rather many outstanding bugs, both for me as an IDE user, and as an IDE plugin developer. Let me give some examples, which should also work as actionable items for people wanting to improve the state of things.
It affects me constantly, because it affects me every time I debug. Basically I had to live with the fact that my debug toolbar has to stay on the far left side of the workbench toolbar, I basically had to learn to live with it for the last year or so. This was reported in 4.4, not fixed on 4.4.1, and not fixed in 4.5 (Mars) either....
(originally a comment on Doug's blog)
Going back on the issue of IDE plugin developers, let me pick up this comment from Mickael Istria:
