I don't see a tracking of severity distinct from priority. Considering that priority has no universal meaning, but only a per-component meaning (at best), this seems very inappropriate for a disperse project like ours.
http://c2.com/cgi/wiki?DifferentiatePriorityAndSeverity
Moreover, the main use we make of "Priority" in bugzilla, i.e. how hard/expensive a bug is, is already covered by "Points".