According to Wired.com "[I]f you’re running it in a browser, Amazon Instant video, Hulu, Rdio, and HBO Go all just work. As did video from Wired, Gawker media, and Flickr slideshows." I have a Roku and love it, but I also have Comcast. That means, in its infinite retardery, I can not watch HBO Go on my Roku. If this really does work as well as Wired says it does, I can watch it through the Chromecast Chrome browser, making my Roku a paperweight.
Roku only makes sense if you're a Time Warner Cable customer and you buy one the nicest Roku models, which of course makes holding onto your first-gen/second-gen Roku (for who knows how long) a no-no becuase these don't support Time Warner Cable's app. Having a Roku is a must in most newer Time Warner Cable markets (such as Louisville KY, where I live) because the ability to offer more HD channels than what you'd get through the cable box.