Oh, I don't think that my WM is ever in the way, although I'd love it if when KDE 5 does ship, there's an option for tiling on the virtual desktop for all the terminal windows. And, I'd say in many cases, widgets are useless, since one would have to minimise windows of useful stuff to really do anything with them. However when I have one virtual desktop that is exclusively for things that can be useful to access, and I can do so with a simple key-chord, and quickly switch back to work without taking my hands off the keyboard. It's faster after all, to find out current temperature and forecast say, to just hit ^F2, look, then hit ^F1 to get back to what I was doing than it would to be to open a new tab, and type in a search query (switching applications, if required). And even less time than say, check RSS feeds by using alt-tab until I get to the right program, or drag the mouse all the way to the system tray to check RSS feeds for anything interesting, since again, it's two key-chords, one in, one out.
The rest of it, really, is just my own sense of aesthetics. I don't really care about resource consumption, especially even with all the candy, X, Plasma Desktop, and Kwin are together at <1% of one core, and using no memory to speak of.
Edit: I think any further discussion along this line should probably be quoted and sent to the *nix thread.