The only different between this and Chrome is the icon. :P
Just kidding. But ignoring ideological issues about open-source and whatever, the differences between Chrome and Chromium are barely noticeable to a normal user. Featurewise, there isn't much discrepancy between the two. Chrome includes built-in support for MP3s and some other proprietary stuff, so certain Chrome extensions that require this support might not work on Chromium. Also, Chromium includes a couple of small extra features that are normally only available in the beta versions of Chrome. However, most of these extra features are "experimental features", so they're not even enabled by default-- you have to type about:flags into your address bar to activate them.
To sum it up: Chrome and Chromium have a few differences, but if you're a normal person, the biggest difference between the two will still be the color of the icon.