What are the benefits of flashing a router with third-party firmware?


I’m considering buying a new router and am currently looking at the Asus RT-N12HP.

A lot of the reviews on Amazon recommend flashing this router with Tomato third-party firmware. See here: http://www.amazon.com/ASUS-3-In-1-Wireless-Router-RT-N12/product-reviews/B00DWFPDNO/ref=cm_cr_pr_viewopt_kywd?ie=UTF8&showViewpoints=1&sortBy=byRankDescending&reviewerType=all_reviews&pageNumber=1&filterByKeyword=tomato

What are the benefits of using third-party firmware on a router? Is it worth the risk of bricking it?