The Nexus Q is Google's first media streamer, a sphere proudly made in the U.S.A. that streams audio and video to speakers and/or TVs, using an Android device as a remote. It's also horribly restrictive and limited in functionality--but it has potential, providing either Google or industrious hackers put in some hard work.
Media streamers have proven a surprisingly hard gadget to get right. There's no one gadget that's easy to recommend for everyone--typically, you'd say an Apple fan should get an Apple TV, techies should opt for the Boxee Box, DIYers should go for a home theater PC, and those who want something cheap and simple should get themselves a Roku. The newest Roku, the Roku 2 XS, suffered from some connection problems, but it's still a very competitive and capable streamer--and most importantly, it's still easy to use.
Apple's new Apple TV has been overhauled. It's been shrunk to a tiny black square, with a new interface and some great new features. But while it does some things very well, it's severely lacking in both content and functionality.