Maybe it's time to be cautiously optimistic again.
When Unity came out, I gave it its 21 days[*]. After that time, I was still not very happy with it, so I figured that after using Gnome 2 for a while, it was time to give KDE another chance.
Well, I'm glad I did. There are still little niggles here and there if you look up close, but as a whole, things work pretty darn well. They've finally managed to return to that KDE sort of state from the 3.5 days, where multitudes of little features activate as needed to support your workflow and otherwise stay the fuck out of the way. Klipper is still so freaking convenient that I miss it sorely wherever I don't have it (the Gnome equivalent, Glipper, unfortunately didn't work very well for me). Also, Chromium now natively supports the KDE password storage thing. Quassel is like a smoother X-Chat with less bugs.
All in all I've been somewhat pleasantly surprised, and I think I may keep it after its 21 days. There are still things that annoy me -- their overthought Akonadi thing, for instance; seriously, guys, I shouldn't need an RDBMS to freaking read mails -- but much fewer so than I feared. Maybe it's time to be hopeful again for that Linux desktop thing we've been hearing about.
[*] When trying out a new tech, you've got to give it at least three weeks of real use, it is said; otherwise you can't necessarily tell if it sucks or if it's just different from what you're used to, and thus, uncomfortable at first.