I'm a long-time mailpress user and very curious how your plugin compares to it.
I've had a quick look and here is what I am missing from Knews:
- option to set up batch sending, i.e. send 50 emails at a time every 5 minutes
- bounce system? needed to keep a mailing list clean
- subscription settings to allow subscriptions to different newsletters i.e. per category? I see you have an auto-create newsletter option but how about being able to limit that to a specific category?
- create a newsletter from an existing post?