So, after reading the above success stories I decided that, as a good starting point for 2015, I would install CSSU thumb on my primary device.

I did it yesterday. It was a bit of a mess because HAM didn't actually do anything other than having apt-worker do whatever it thinks it was doing until it stopped. I never got the "Community SSU" icon in the apps menu.

In the end I started installing some of the many packages proposed by apt-get upgrade until I felt confident enough to let apt-get upgrade everything, which it did. Rebooting worked fine, which kinda surpised me, if I'm honest.

I'm at a point where apt-get upgrade doesn't want to do anything (good), but the meta-package mp-fremantle-community-pr is not installed. If I wanted to install it (which I don't), I would get:
busybox-symlinks-procps (wants to remove procps, so no way).
community-ssu-enabler (I guess this is the "icon" referred to above)
hildon-welcome (don't want it)
libcpaboutcssu (what's this?)
libqt4-* (unnecessary packages unless something depends on them)
maemo-optify-runonce (be gone, and stay there forever)
modest-home-applet (don't want it)
pulseaudio-esound-compat (don't want it)
qtm-maemo-metapackage (as long as noone depends on it, I don't want it).

If there's a good reason why any of the above should be installed, I'd like to know.
Other than that, CSSU thumb works fine and it does feel snappier (but this may be just because I let apt-get replace by transitions.ini with the maintainer package).

The only negative effect possibly directly linked to CSSU is that my first alarm this morning stopped after a second or two without me having touched the stop or snooze button. I had experienced this in the past, but not for a long time. I'll keep an eye on it though.

[EDIT] To clarify: it auto-snoozed. Meaning 10 min later my second alarm (which happens to be 10 minutes after the first alarm) popped-up OK and when I closed it the first alarm (the "auto-snoozed" one) popped-up.

Oh, and for the rotation I had to enable the accelerometer module which I had disabled in MCE a long time ago. Now my desktop rotates. I have to learn how to deactivate that

Cheers, and thanks CSSU people.