Great short and to the point post. I have been using email newsletters for sometime now and have had some great results for some of my clients also.
I only use Aweber, and have had an account with them for the last 3 years and would recommend them 100%.
Some interesting questions above, may I offer what strategy we use?
We make sure that we load the auto responder with at least 6 months of content that is not time sensitive or season based, so it does not matter when someone joins or in what year, I suppose it was our first discovery of the importance of “evergreen” content – always relevant.
We never try to sell anything off this auto responder series as it is about top content relative to the audience, and we want to build great trust.
We will then use a broadcast email for seasonal (Christmas etc.) greetings/announcements or timely info that is relevant to now ie. Google Panda alert. And for any list only special offers or promotions.
Not saying it is right or wrong, it is just the way we do it