See e.g.
http://milkyway.cs.rpi.edu/milkyway/result.php?resultid=758337201

Boinc runs on niceness 19 on my system. I think this is reasonable. However, it seems the milkyway tasks attempt to set priority to 0, which fails.

I guess that attempt to an priority upgrade is an error in the first place? If there is a reason to run at higher process priority than "background" please tell me, maybe I can find a way to make that work.