All the fonts are look beautiful and even the normal fonts like Arial and Verdana also looks good for reading, because it was specially designed for web pages. All fonts in the fonts in the Google has Open Font license, that means you can use in any commercial purposes without any restrictions.
How to download Google fonts to your computer:
It's open for all, to download Google web fonts and use it to their computer in MS word, Photoshop designs and in PDF's. There is no trick evolved and you download and use like other fonts.
Just go to Google Web fonts, explore around which fonts you like add to collection and then you can download fonts by clicking the link at the top right corner named "Download Your Collection"