While this plugin works to make widgets visible or invisible, it fails to work well in any environment where there are regular updates. The reason for this is exceedingly simple (so much so that it is surprising that the developer hasn't identified this problem...almost as if they've never tested the plugin in a production environment of any kind): widget visibility cannot be set to off by default.
This means that should you place a widget and set it to be only visible on a couple of pages everything will work perfectly well right up until you write a post or add a page. At that point, the widget will be immediately visible on the new post/page.
This plugin will work perfectly for people who are looking to create a static, or seldom-updated site. For those people it is likely a 4 or 5 star plugin. For the vast majority of users—who will be regularly adding content to their wordpress sites—this plugin simply adds work to every update cycle. And the more you utilize the plugin, the more work it adds to your cycle. (Imagine you have a dozen widgets meant to be visible on just a few pages. That's a dozen widgets that must be edited every single time you post.)
[Apparently the text of my first review was deemed not as useful as the one word five star reviews and was removed, so I'm just going to write another one. Hopefully the mods will be able to see the clear issues with the plugin and don't cater to the plugin dev who, of course, would rather not have me explain why their plugin is deeply flawed. But the USERS who are looking at this plugin deserve to know the truth about the rather severe limitations it has. Perhaps a new update to the plugin will add the simple functionality required to make specific widgets default to invisible. Until then, this plugin is exceptionally poorly suited to any real production environment.]