Creates a unique, persistent geometric icons avatar for each commenter based on email address.
Yes, if they're using the standard version (and I didn't mess up anything).
Yes. Just turn on the Gravatar option in the Identicons options page.
Yes, this plugin provides a replacement widget to Recent Comments (since the default widget doesn't provide the commenter's email).
Yes, just select the WP 2.5+ Theme option to the Automatically Add Identicons setting in the Identicon control panel.
The gravatar identicons are pretty good but if you want more control (custom colors, transparent backgrounds, different numbers of blocks) or just want one set of avatars for everyone on your site, then this plugin's for you. Otherwise, sure go with gravatars (just set
&default=identicon in the gravatar url).
Probably (if I have time/know how). It's definitely worth a shot since I'm always looking for feedback on how to improve my plugins.