We now have a JIRA project available at https://issues.apache.org/jira/browse/MAHOUT
General rule of thumb that helps us prioritize, etc. Discuss any "bugs" on the user or dev list first to confirm they are indeed bugs, then put them into JIRA.
It is also a good practice to put all but the most trivial of patches into a JIRA issue before committing (I think it is safe to exclude most documentation issues) so that others can review and also so we have some history to tie it together. I also try, when closing an issue, to put the SVN commit revision in the comment on JIRA (although, I think JIRA does have some integration with SVN as well)
-Grant
