Apps that are just a trimmed down Safari are annoying and pointless. However, there are tons of apps -- especially apps for news sites -- that offer a lot of additional functionality, such as better control over font size, much better navigation and customization, the ability to save local copies of articles, etc. It really comes down to how much effort was put into the app and how often you access a particular site. I bet just about everyone has at least one or two sites that they would prefer to use a well written dedicated app for.