Well, I can only compare with the script above, since that is what I am loking for:
This script checks the WPMU database for blogs that have
not been updated for X days, then sends a notice to the
blogowner that the blog will be deleted after Y days.
=> your plugin does just that
It also automatically deletes blogs that have not been
updated for Y days, then sends an email to the blogowner.
=> your plugin can do that
On both occasions, the script will send a report with
details on warned and deleted blogs to the administrator.
=> this would be nice to have
AND here is another question: what exactly does "inactivity" mean?
(How long before a site is inactive?)
Do only new posts/pages count? Does updating posts count? Does logging in count? If you want you could give us an option to chose what we count as activity/inactivity, i.e. in some cases you might want to count any activity, even logging in to be enough to keep a blog active? Just some random thoughts on my part :-)
Thanks again in putting this plugin together and developing it!