FontBottle was created for Mac users who wish to preview the fonts that are installed on their computers. This utility comes as an alternative to using Mac's default font manager (Font Book) to check text styles, is very simple to handle, and has an integrated search tool.
The application has an intuitive interface that's divided into 3 columns. You can add your own text in the first panel, choose from multiple font styles and sizes, zoom in the written words, etc. The program also provides you with a fullscreen option which can be enabled from its main menu.
By clicking the "Aa" button from the upper side of the screen you reveal additional options. From there you can select the preferred font style, text color, browse font families, and print the text content.
The difference between the default Mac font viewing program and FontBottle is the fact that they have distinct interfaces. They both provide you with a list of all installed fonts, come with built-in search tools, and let you preview the text styles in various sizes. So, I can't find any reason why I would install FontBottle on my Mac when I'm already having a program that works perfectly and offers me all the features I could possibly need from a font manager.
Nevertheless, FontBottle is free of charge. So, it's up to you to decide if it's worth downloading it on your computer or not.