Dear fellow RIOTers,
as there are still issues with our timer subsystem, we've concluded to create a timer task force in order to sort out the issues still popping up. Up to now, Hauke and I (possibly someone else?) have just collected initial facts/requirements/ideas in a Wiki page:
https://github.com/RIOT-OS/RIOT/wiki/Timer-Task-Force
If you'd like to be part of redesigning the next iteration of RIOT's timer subsystem, please say "Me!" and add your thoughts to that page.
Feel free to discuss any aspect using this list. 
I'd like to collect input for maybe another two weeks and then have a (face-to-face) meeting if needed to iron out the next steps.
Kaspar