First, the results: I use AutoTweet for a very specialized professional network (nonprofit marketing specialists). Within a few months of using AutoTweet, our Twitter feed attracted hundreds more members to the network.
Setup and Operation: The commercial version was fairly easy to set up and configure. I like the way that it reports on the status of each tweet or Facebook post, so I can quickly tell if I am having problems.
Level of support: When I had questions about tweaking the configuration, the support was timely and informative.
Performance: This has been one of the few components that have been "set-it-and-forget-it." The only performance issues I run into come from my own changes to other parts of the site configuration without telling AutoTweet what I have done.
In summary, this is such a great component, I hesitated to write this five star review because I have thought about it as my secret weapon. But in the spirit of the Joomla movement, this component and its developer deserve to be praised loudly and widely for the excellent work.