While tested out Discourse, I only found a few negative things:
- To make it act like a mailing list, it currently requires each user to change settings on their account: https://github.com/discourse/
discourse/blob/master/docs/ MAILING-LIST-SETUP.md# suggested-user-preferences
I commented on a thread about a new feature that allows setting defaults for this: https://meta.discourse.
- It doesn't allow setting defaults for which categories the user has "Watched". For example, I would want to default the "General" list to "Watched", but more obscure lists would only be watched if the user chooses to.
- It uses a different e-mail address for each e-mail it sends you (this is to keep track of which thread it belongs to), here's an example of a "From" address: testdiscourse+
Google Groups always has the same to/from e-mail address and magically figures this out. This might be weird in some peoples' email clients.
As a forum, this beats the crap out of PhpBB, but as a mailing list it's not a clear winner over Google Groups yet. It's open source, has a better web interface, and the "Categories" are a cool feature for keeping all the lists in the same place. But, the "email in" functionality was too recently implemented, and it might take a few months before it's as polished as Google Groups.
It's going to be a very tempting replacement if they add default settings for user preferences.