As your latest update is from 2009 and from what I can see it offer very simple sign up form and can only be manually installed.
As you said, can be used as a staring point.
Some features I would like to see:
Sign up form
Can be added to a block
Can be used as an Ajax slide in or pop up when entering/leaving the site.
I like to know where my subscribers are coming from,
Forms, same or similar as when you sign up to glF. Make option to add forms such as country.
Fore those marketing to local market could us State/City/Town etc...
Text editor like the one I am using right now or similar!
Can use/import ready made e-mail templates and store them for later use.
Manually add names and email addresses, import/export as .txt and CSV
When sending your letter, as in glf, option to send to groups and/or country etc.
(makes a huge difference when sending special offers/news to a targeted market)
There's a "themefiles" directory in the plugin archive that I think needs to be copied under your layout directory. The directory contains a "newsletter" subdirectory, so you should end up (assuming that you use Nouveau) with public_html/layout/nouveau/newsletter, and the templates will be in there.
I don't know if that's the only difference, but it's one that relates to your current issue.