Having worked on projects that have a commit notification mailing list available, I strongly advise to have such a list anytime you have more than one developer working on a project. Bonus points if every commit message comes with a bundled copy of the change's diff (in unified form!). This list must be independent from the regular development mailing list and it must be opt-in: i.e. never subscribe anyone by default, let themselves subscribe if they want to! Not everyone will need to receive this information, but it comes very useful... and it's extremely valuable for the project managers themselves!
Why is this useful? Being subscribed to the commit notification mailing list, it is extremely easy to know what is going on on the project. It is also really easy to review the code submissions as soon as they are made which, with proper reviews by other developers, trains the authors and improves their skills. And if the revision diff is inlined, it is trivial to pinpoint mistakes in it (be them style errors, subtle bugs, or serious design problems) by replying to the email.
So, to my current project managers: if you read me, here is a wish-list item. And, for everyone else, if you need to set up a new project, consider creating this mailing list as soon as possible. Maybe few developers will subscribe to it, but those that do will pay attention and will provide very valuable feedback in the form of replies.
1: Shame on me for not having such a mailing list for ATF. Haven't investigated how to do so with Monotone.
2: Of course, the developers must be conscious to commit early and often, and to provide well-formed changesets: i.e. self-contained and with descriptive logs.