In the MIDI options, (auto) should be the default timer, not hrtimer. I struggled for 2 days trying to figure out why Rosegarden would not send MIDI notes when all other programs would before randomly discovering that setting this option to (auto) or "system timer" corrected this problem.
This goes to usability. While people like me will probably eventually figure it out, a lot of people would not. Plus, different systems use different timers (I have an rt-kernel that uses an rt clock, not hrtimer), so (auto) is simply a much better default option.