Google Android Senior Product Manager Erick Tseng told the media crowd during the event that the Nexus One is the first of an emerging class of devices it calls "superphones," partially because it's unusually fast, running the 1 GHz Qualcomm Snapdragon processor. This enables the smartphone to run several Web applications seamlessly at the same time.

"It's just really fast, especially if you've got multiple apps running simultaneously. You've got your music running in the background, you're syncing your e-mail, you're broadcasting your location to your friends using Google Latitude and meanwhile you're browsing the Web. If you've got all of those applications running in parallel on some other smartphones, you might start seeing some slowdown. With the Nexus One, you see a lot less of that and that's because of that really fast processor under the hood."

The Nexus One runs Android 2.1, which includes Google Maps Navigation turn-by-turn GPS; support for multiple Gmail accounts, universal inbox and Exchange support; and the ability to aggregate contacts from Facebook and send Twitter tweets.

Android 2.1 also enables the Nexus One to offer a voice-enabled keyboard that lets users speak into any text field, to conduct text messaging, e-mail writing or search querying without typing. There are also live wallpapers and a 3D photo gallery, among other features.

Also, the Nexus One supports Google Earth, a first among Android phones, as well as Google Voice and other standard Google Apps.

Tseng noted that the device also uses two microphones to employ dynamic noise suppression from Audience, which means the Nexus One filters out background noise when users make phone calls. There are also several sensors on the device, a compass, accelerometer, and light (adjust power use) and proximity sensors (prevents accidental touches on the screen).

The device also has a track ball with tricolor LED, alerting users to new e-mails, chats and text messages. Users may also opt to have Google etch personal laser engravings on the device.

Other features include the 3.7-inch display, which matches the Motorola Droid in size. However, the Nexus One display is a 480-by-800 AMOLED (active-matrix OLED) design, boasting greater contrast and brighter colors.

The phone is thin, only 11.5 millimeters, and weighs 130 grams, far lighter than the Droid's 170 grams. Nexus One boasts a 5-megapixel auto-focus camera with flash and geotagging. Users can take high-resolution video in the MPEG4 file format and upload it to YouTube with a single click. There are 512MB of flash memory and 512 MB of RAM, expandable to 32GB.

Walt Mossberg has a full review at the Wall Street Journal here (paywall warning), but there is a lot more to read on Techmeme here.