When we start our browsers, we have to have a default page that opens open first, so it might as well be something filled with useful information.
It's Google... really, what else can you say about it? We all know it, we all use it, it's now an ubiquitous part of the Internet. You can customize it with widgets as you see fit, and use it as a central hub to get to all of the other Google products. The biggest complaint folks seem to have about it is the plain whiteness of the background, but it appears they are working on that finally.
With the slogan "(re)mix the web", the moniker proves to be true. This start page is like the ultimate RSS reader that you can mix and match as you choose, and they are constantly adding new widgets to make it even more useful.
A highly customizable start page where you get to pick the categories you want from the get go with no presets. They are even releasing specialized educational widgets to make it as user specific as possible. Considering how young this page still is, there's no end to the potential industry specific widgets they may launch.