Very useful plugin, thank you.
Two issues, the first is far more important to me:
1) It would be great if the notification e-mail could include the recent changelog for the plugins with available updates. Checking the changelog is the first thing I do - to check any incompatibilities, see how urgent it is (is it a security update?), assess any likely impacts. So, every time the updates e-mail comes, I'm off to Google to type in "Foo WordPress plugin changelog".
The WP update mechanism has this facility, so I'm presuming there's code that could be re-used from there.
2) The update notifier always fires before I've had a chance to configure the plugin - resulting in an e-mail going to the e-mail address before I get a chance to change it. Once I changed the site address first to try to stop this (it confuses the site owner when I'm managing the site for them), but it still went to them so I'm not sure where the plugin is picking the address from. But in any case, it'd be handy if the first e-mail didn't go out so quickly. e.g. Check if 15 minutes have passed since the plugin was installed?
Thanks for considering these.