I am familiar with subscribe2 per installation for a client, but I am slowly falling in love with this plugin myself.
The only extra feature that I wish the plugin would have is availability of a blog user side's option to chose between weekly digests and "per post" email notifications (I guess other available time frames for notification choices can be added as well).
My client's issue on this was that while trying to be as not intrusive with his subscribers (1K+) as possible, he is often at the dilemma of going with "per post" notification or weekly digests (depending on how many publications per week he is making) or the weekly ones. He currently keeps switching back and forth, but the preference is to let subscribers (blog users) to chose the frequency by themselves.
If that matters, he has the "Automatically subscribe new blog users" setting to "On".
If adding such choices is not to be implemented as feature for of the whole plugin, I would appreciate an advice on code modification. It seems that it is just a matter of "transferring/enabling" the admin's side digest frequency radio buttons, to user's interface.
Thank you in advance.