Taken from an exchange on the TextMate mailing list:
Allan's reply (edited by pbx):
My preference depends a bit on the type of bug report. Here are some hints:
If it's a problem likely introduced in a recent build or affecting a lot of people. I.e. stuff that potentially could lead to a lot of duplicate reports.
For bugs where the reporter is unsure if it's really a bug, by- design, or maybe something else interfering, should preferably also go to the list (since others may be able to answer it, and save me some time).
For everything related to bundle items, since a lot of the stuff is done by other TM users (who for the most part are subscribed to this list).
If it's crashing or acting in some way that it really shouldn't (e.g. refuses to open some document). Logic being that this is probably a case where I need more info, and little is (probably) gained from reporting this in public.
For everything else :) that is, stuff that's not affecting stability, and not a real problem for using the application.