Take a look at the reviews for the app entry in the Android Market. They will all be about the app, and can likely tell you more than we can. As for whether paying for apps with a credit card is safe, I would say yes for two reasons. Firstly, I think that Google only lets you pay for apps with a credit card anyways. In addition, if you don't like an app after buying, there is a limited time period in which you can uninstall the app off of your phone and have the money refunded back to your account.