The ease at which to implement this plugin is great! It was very easy for me as I am not highly skilled in coding, but it's also user friendly if you do have some experience using HTML/CSS or even PHP (which we don't).
There are no downsides that i can see about having conversion alerts implemented into our site because they're pretty much foolproof once set up correctly. What I really like most abut these plugins however - apart from their functionality-is how simple they make adding social buttons onto pages. We use them mainly just for Facebook likes etc so there isn;t anything more complex than that involved here.