They work when they want to, but leave very much to be desired.
POWr apps take you out of the shopify experience and force you to edit then through a separate popup.
Additionally, since the content entered through their apps resides on outside servers, if their servers are unavailable, which has happened to us several times, you have a big hole in your page, plus to drags the page load time way down.
For these reasons, we have had to remove all instances of their apps from our home page on http://shop.dronecyclone.com We are quickly losing patience with the risk that their apps present. We are in business to be in business, and can only use apps that are 100% reliable. Sadly we have had two significant failures of their servers in 3 months. Of more concern is that they do not provide any elegant failure - they just leave it up to the browser to tell use if we happen to be on our site - how do we really know how many times it fails???