I put a copy of this mail to the devel-mailing list, so others can use this information as well. Hope thats ok?!
We do not use the Systick-timer for two simple reasons at the moment:
- RIOT uses a tick-less scheduling paradigm, which means that we do not have a regular system tick that wakes up the scheduler to see if a new task needs to be scheduled. But this is what the Systick-timer is originally designed for… You can refer to  for more information on this.
- RIOTs hwtimer needs best to be able to set more than 1 timeout in parallel, so the peripheral timers with more multiple capture/compare channels provide a better base for efficient implementation than the Systick-timer…
But you are certainly ok with using the Systick timer for your specific implementation, there is no reason not to use it…