I see 4.x as being a pretty big failure. I use it everyday and there are a number of things that really annoy me. Especially things that used to work in 3.x and now don't work well (or at all). I have reported bugs for the more egregious ones, many many months ago. Nothing whatsoever has happened with those. So what this tells me is that KDE's vision is clearly not following the same path as the way that I like software to behave. Their priorities lie in making things new and flashy, regardless of whether it's done well. They also just push out stuff that isn't properly configurable with defaults I hate, which is completely contrary to the original KDE ethos "be configurable". Like why the f do I have to right click on a process in the task bar and select Do Not Allow This Program To Be Grouped every f time I start my desktop and open two firefox windows???
Things like that, which are completely trivial to fix, seriously kill the user experience.