This plugin helps you to keep the link juice by redirecting all non-existing URLs (they return error 404) to the blog front page using 301 redirect.
Seems to work on with multisite 3.6.1. I did not network activate, and it works on my main domain and all other sub sites work as normal. My sub sites have the option to activate, and it seems to work for them individually as well. Seems to be a great plugin but I need to do some further testing to make sure it's stable. I will post a followup if I find a problem.
As a side note, the author should at least ensure proper coding standards based on WordPress 3.6.1 and update the plugin! I know some hooks are being phased out and an update is probably seriously needed before 3.7 drops
I am currently using the plugin to keep link juice I'm getting from PR domains I buy. It redirects all non-existent pages to my homepage and does a great job. I have it on ALL (258) domains. Best of all it's FREE!
Very useful plugin for keeping the link juice of my sites.