You need some time to find your way with this plugin, the description texts are sometimes hard to understand for a newbie (especially if you compare it to wysija for example). But after you got familiar with it, it is really cool to have so many settings options.
You are very flexible in writing newsletters that match your needs. The only reason I give 4 stars only is the user management and import: grouping subscribers (especially imported ones) in groups/lists would be important for many scenarios (similar to wysija).
(oh, and it would be cool to hide the web version link in the web version ...)