What this plugin does, you can pretty much do yourself with icontact's provided form code.
What this plugin doesn't do, and would be really nice, is to use AJAX and the full iContact API to handle the contact submission form and display the response right in the same div on the same page, without redirecting you to another page. As it is, you must make do with iContact's own success/fail landing pages, or ones you designate yourself, on your own site, or no response at all.
I think with the state of the web in 2013 people don't like being redirected to another page just because a programmer didn't write the ajax. They want to sign up and continue browsing where they left off. Mind you, I can't write it myself :(... And I used this plugin for two years satisfactorily.
But for smooth feeling signups, Easy iContact is a better plugin.