To be fair KDE4 _was_ a disaster when it was released but in time it came to be as stable and usable as the much loved KDE3.
The path to plasma was also somewhat rocky (but nowhere near as bad as the KDE3 - KDE4 transition).
I used to enjoy using KDE but I feel they lost their way and are overly attracted by "shiny new things" like workspaces, activities, or semantic desktop - virtually everything being dependent on strigi then akonadi then nepomuk then baloo or ...
The real bugbear is that every time they ditch everything for a new metaphor - so much of the previously working and reliable software is also ditched or obsolete.
It doesn't suit my needs to have to keep re-configuring my computer and software and workflow so I stopped using it.
I do think it's great and valuable that it's there as an option though.
Akonadi was the main reason why I ditched KMail for Thunderbird six years ago. I recently went back, and it's marginally better. But it's still pretty outrageous that a service that only gives one user-visible extra feature (mail checking and calendar reminders as a background service) costs 330 megabytes of RAM. Most of that for the MySQL instance that it's using; no idea why they have to use anything else than SQLite for a mailbox with maybe 100 mails. Stopping Akonadi is a thing that I just have to do before launching Minecraft on my notebook.
$ free; akonadictl stop; sleep 15; free
total used free shared buff/cache available
Mem: 3934720 1227872 1296492 253868 1410356 2203068
Swap: 0 0 0
total used free shared buff/cache available
Mem: 3934720 897308 1626924 249452 1410488 2538072
Swap: 0 0 0
I'm still sticking with KMail for now, though. The UI is a bit nicer (esp. w.r.t. GPG), and mail checking as a background service is nice.
