It is a great program. I've used it for a really long time. I'm not for certain if the problems I'm having are with the new version or with dreamhost.
It is dealing with batches, sending so many messages (through sendmail) every X minutes, so the server doesn't get overloaded.
I had a list of about 1500 subscribers, me being the last person on the list, and I never got the message. I know some users are getting the messages, because I get the "out of office replies."
I tested it with a small list (4 users, with the batch set up to send to 1 person every 5 minutes) and it worked, as far as we all got the messages. I didn't receive the batch e-mail updates that are usually sent, (which could be a bug with Dada). I'm going to post a message on their support board.
I DO recommend the program, and if you want to make sure it works, you can pay to have it installed (which I think includes updates for a year -- I may be wrong on that, though).