What is it?
It's an orblike streaming-media device, selling for $300 and shipping in mid-July.
The Nexus Q is shaped like a very small bowling ball and is almost as heavy. It's got a flat bottom for setting on tables, but is otherwise a smooth matte black. When you turn it on, a middle strip glows with LED lights to indicate that it's working its magic, streaming songs, videos, and photos to your connected devices around the house. When the lights glow, it looks like a small Saturn.
On the back, there's a Micro-HDMI output, an optical audio port, Ethernet jack, plus a Micro-USB port for "general hackability." More interestingly, there's a set of banana jack speaker outputs, which are for powering speakers using the Nexus Q's built-in 25-watt amp, no separate AV receiver required. There's also built-in dual-band Wi-Fi, Bluetooth, and NFC (near-field communication) support.
The Nexus Q runs a version of Android 4.0, with 16GB of onboard flash memory and 1GB of RAM. Unlike streaming-media boxes like Roku or the Apple TV, the Nexus Q only supports a few Google-centric apps: Google Play Music, Google Play Movies and TV, and YouTube. The "social" aspect of Nexus Q initially appears to be the ability for multiple Android devices to create a group playlist.
Think of the Nexus Q as mix between an Apple TV and a Sonos Connect:Amp.
Part of its functionality is to act as a bridge between Android devices and your TV. Use your Android phone/tablet to queue up music from Google Play Music or a video from YouTube, then have it play in your home theater on the Nexus Q.
However, it operates a little differently than Apple's AirPlay technology. With AirPlay, typically content is first streamed to your phone/tablet, then it's streamed again from the phone/tablet to your Apple TV. With the Nexus Q, the Android device is merely acting as a controller: you tell the Nexus Q what to play, then the content streams directly to the Nexus Q. The downside is it appears that only Google Play content and YouTube will be supported, at least initially; AirPlay currently works with tons of third-party apps.
Why does it cost $300?!
The Nexus Q's price is surprising, especially since the most successful streaming-media boxes (Apple TV and Roku) sell for $100 and less. A lot of that cost is likely because of the built-in amp. The similar Sonos Connect:Amp also features a built-in amplifier and costs $500 -- and the Sonos only supports music. Also driving up the cost may be the fact that the Nexus Q is manufactured in the United States. (The New York Times has a more in-depth look at the manufacturing process.)
Still, I think Google is going to have an uphill battle convincing buyers that the Nexus Q is worth $300, especially since it currently only supports Google Play content (no Netflix, Pandora, etc.) and only works with Android devices. That seems like a small niche with not enough functionality, no matter how well it works.