What is the best PHP mailing list software?

In my search for the best PHP mailing list software, I’ve come across some pretty bad ones, and some pretty good ones.

My criteria for a “good PHP mailing list” is the following:
-easy install
-easy integration
-double opt-in subscription
-sends mail even after browser window has closed (imagine waiting for your PHP script to finish sending an email to thousands of subscribers, one at a time).
-customizable admin interface
-open source (and free!)
-not a hosted solution

That may be a dream, but I just found a new PHP mailing list that may meet the criteria. phplist.com may just do the trick. I will try it out and let you know what I think.