Well, yes and no. Since a latest post plugin or listing of blogs are not a standard part of MU, you (or someone else) have to make such a plugin. So the author of such a plugin has to build in support for the kind of Avatars he or she wants the plugin to support.
On the front page of my MU site, I've made two plugins. One that show a random post that only use Gravatars, and one Widgetish plugin that show the latest post from 10ish blogs that also just support Gravatars.
My thought behind this (and the standard version) was to use with comments, and thus to utilize the different kinds of (gr)avatars in the comment section of blogs.
The rest of the functionality is due to my needs (I know thats kind of an ego trip...).
So basically what I'm (trying) to say, is that this plugin is not trying to be all powerful, but just to serve the needs for (gr)avatars in the comment section and a few other (useful?) things.
And last, there is nothing wrong with utilizing the code from this plugin to make it coexist with other plugins. All of the code is GPL'ed so anyone who wants to make a go on it is more than welcome :-)
Just for the record; I would love to see a built in system that make use of OpenAvatar, Gravatars, Identicons, MyBlogLog, Favico and user uploaded avatars - both in standard WP and in MU ;-)
Best regards,
Rune