I'm a WordPress user for years and WordPress Mu too. I love WordPress and I'm almost comfortable with codex, etc. But now I need help :)
Some years ago I tried to create a custom wordpress page for an old version of WPMu. In that moments I was looking for a more complicated solution. I found the solution but now a days it not working. So I need to find a new solution to my needs, and hope my needs will be more universal than personal. And the best part of it: it's easier than then because I don't want all that things.
I want to have a custom home page on the network main site. This home page must show the last activity in all the Network in this way:
1. Show Avatar/Author name/Title of each blog
2. Show only the LAST post of each blog (Post title, date & intro - linked to the particular post) on the Network beside it's avatar/author-name/blog-title.
3. If it's possible, but not a must, show number of comments on each post.
This info must be shown on individual blocks. Is not necessary that last post, and so its blog info, is going to be on the top of the list but if it's possible it could be a great point! :)
In this way we can have a custom home page on the root with all the activity on the Network.
I found this solution on the forums http://wordpress.org/support/topic/multi-user-home-page-aggregation?replies=4 but it's not a complete solution because only displays the blog who was updated.
Finally my idea is use the custom loop-index.php file to add the code that helps us to have this custom homepage.
THANKS IN ADVANCE FOR YOUR HELP! ;)
ps: Non profit project for a small Blog Network site based on Spain.