I use KDE as work and at home. I've considered changing to i3 but there are just so many useful features to KDE (especially on a multi monitor system)... I'll admit I was a bit more enthusiastic about the DE back in KDE 3.5.10, but now I don't think I'd look back all that much.
I'd hope that the KDE team would consider another rewrite in the future. I think they have the right talent to create something that is high performance and truly minimalist, but also, modular and full featured. Plasma, while very responsive on newer hardware, "feels" a little heavy regardless. (I'm pretty excited about the RazorQT project)
One thing I wonder why they didn't do was porting KIO to FUSE or something. There are lots of great KIO plugins that would be more useful if they were transparent to the application.
Also: Anyone else find the keyboard/mouse bindings available in KWin not even close to as functional as Compiz?