I can configure the desktop to be more useful than just being there. For example, I work with a lot of LaTeX documents, in particular folders containing tests and assignments for the classes I teach. So I have a desktop with a set of folder view plasmoids pointing at this folder full of assignments. One view is filtered to show only .tex files, and the other view is filtered to show only .pdfs. Super convenient, better than popping open Konqueror (or Dolphin) and navigating the folder, even more convenient than popping open a terminal. Way nicer than the garbage dump of "maybe I'll need it later" files that desktops usually are.
Similarly I have a desktop full of folder views and other plasmoids that are useful for my research, a desktop full of folder views and plasmoids useful for coding, et cetera.
This is something I can't do with any other desktop environment, and I've looked. (Well, actually there's a couple of proprietary Windows 7 add-ons that give similar functionality, if I felt like forking over the dough. And using Windows 7.) And other than the desktop itself, the auxillary applications (the ones I use, at least) are all at least as good as they were in KDE3.
Also, KRunner (Alt+F2) with nepomuk is awesome. File search and program launching, yeah, every desktop is decent at those nowadays. But there's a lot of useful KRunner plugins too. Calculator, dictionary, spell-check, search wikipedia, mini command-line shell; it even has a task manager so if a process is misbehaving I don't even have to open a terminal and use htop (unless I'm in the mood to use htop.)
Give it a try, man; it's actually pretty great. And as far as eye-candy and bloat go, I do all this on a four year old netbook. I didn't even disable any of the eye-candy. What bloat?