Garvin has agreed to host this on and already checked it into Spartacus, so it will be available at some point over the next couple of days (usually 24 to 48 hours, so maybe Sunday) either using the spartacus plugin or on spartacus.s9y.org. Until then, a screenshot is available.
As you can see in that screenshot, Mimbo uses a different approach to the start page: It displays entries from selected categories (this can be done using the s9y theme options) in three areas (lead, features, and news), each area having it's own, unique look (and, yes, .tpl file). The images accompanying the entries shown in the screenshot are not included in the template, but users can assign their own images to each entry using extended entry properties. Instructions how to set this up are included in the theme options page, which also allows you to customize the navbar and assign s9y categories to the three Mimbo categories used on the start page.
This is not a 1:1 port. I had to drop the fancy dropdown menu as well as some of the sidebar stuff and some other features the original has. This is simply due to the fact that the original is for that other blog engine, and you simply can't port these things with reasonable effort. We may eventually add some of these later, if - and only if - there is a a reasonable demand for them among users.
I have to thank Garvin and Don for their invaluable suggestions and code examples. I also have to thank Carl for doing the Hemingway template, which has been an awesome code example. I can only advise any template designer to dig into the Hemingway code, it's a great learning experience!
YL