Baloo, at least, needs to be sufficiently visible that you can turn it off. It eats up an incredible amount of CPU time to, for me, no benefit. KWallet has it's points, but it's not THAT great. In my use case sticky-notes would be quite reasonable for passwords. Just don't make them accessible over the net (i.e., to other programs running on the same machine). I'm not worried about shoulder surfers. As for Akonadi...I had no idea what it was until I just now looked at the web page, and I still don't know if it is of *ANY* value to me. But if it doesn't take up CPU time when I'm not using it, I guess it doesn't do much harm.
OTOH, I find Gnome3 unusable. Gnome2 was decent...I preferred it to KDE4, but then I preferred KDE3 to Gnome2. xfce would be a good system, but when I tried it, it got confused about which window was on top of which (more specifically, windows tended to get stuck under the menubar at the top of the screen). It's usable, but with several misfeatures, so currently I'm using KDE4. I'm also wondering about razorQT, but I don't want my window manager to be flakey, and the last I heard razorQT was in very late alpha. I've also heard about LXQT recently. Don't know what it's status is, but it isn't in the system repository, and this makes me dubious.