As a gaming fan, this decision pleases me more than Google, even though I'm generally a Google fan. Why? Namely because Google seems to cannibalize and revamp their products, and far from always for the better (hello, mandatory Google+). Plus, it seems like Google doesn't like to let their products do their own thing - it's kind of like Activision where you're now going to do it their way. Amazon, on the other hand, gives the impression that they're in it for the long haul, and will still let Twitch.tv do their thing- only with massive capital to back up their projects.
Regardless, it will be interesting to see how, if at all, the Amazon aquisition affects Twitch.tv.