It is refreshing to use a plugin that is actively updated and bug fixed. For example, when we started using the plugin, they did not have a "View this newsletter in a browser" link and within a few revisions they had added it.
The developers have been quick to answer questions and even put their answer into their FAQ (I wanted to remove the unsubscribe link because we have a custom unsubscribe page we link to in the newsletter itself).
We use this plugin on a regular basis and it-just-works! My client and I like it so much, they have voluntarily donated to Wysija. Dollars are votes.
(@backagain - troll, troll, competitor, troll)