An update of the current process.
We receive on average around 3 or 4 bug reports per day via reportbug, stuck in the mailing list moderation queue.
Then Corey Burger forwards them to me once a day. Every few days I do some basic bug triage on this pile of accumulated bug reports, and file the good/usefu/non-duplicate ones to Launchpad as new bug reports.
I also notify every single reporter that they should use the LP web interface instead. This response seems to generate a range of answers from the reporters; from no response, to "yes I will do it for future ones" to very negative replies expressing the disbelief that Ubuntu would ship with a broken reportbug.