I did a few posts on Single Sign-On between Moodle and Elgg some time back.  Recently, I looked at Moodle Network (MNET) and how well it integrates with other software with support for it.  Since we are interested in integrating Moodle with portfolio and social networking tools, I tried setting up Mahara to "talk" with Moodle using MNET.  Setting it up was pretty easy -- thanks to the detailed guide called Mahoodle.  After I got it working and tested it a bit, I liked what I saw.

Here are my first impressions on MNET and Mahara:

1. As long as the MNET API is implemented on the target software then it is easy to setup.
2. Using MNET, Single Sign-On (SSO) between Moodle and Mahara is flexible enough in the sense that either one of them can be the authoritative server.
3. Exchange is done via keys so it's a lot more secure that passing in plaintext password and encrypted hashes between servers.  Keys are automatically rolled for a predetermined number of days and the public key is propagated to the peers so that is an added layer of security.
4. Using the MNET API, automatic user creation works on Mahara using the Moodle user details.  It's nice that it also includes the profile picture in the propagation.
5. Configuration is very easy.  It's mostly done using a web UI to manage the server details.
6. Mahara supports more than one institution to be integrated to itself. So in theory, one can have a single Mahara install running and integrated with all your Moodle installations.  I haven't tried this yet so I can't comment yet if there are any significant advantages or disadvantages to using this approach.
7. The API is written using XML-RPC transport model so it should be easy to extend.
8. Mahara runs on PostgreSQL and being proponents of OpenACS then this is a plus for us.  And the Mahara developers present a lot of points on why this is the case.

For now the integration between the two is just SSO.  Moodle 2.0 have plans of doing "portfolio apis" so that one can potentially have a "share this" button on a moodle object and it gets published to the integrated portfolio server. That being said, we would definitely revisit this again in the future once more of the features for Moodle and Mahara integration are in place.