The dedicated navigation and action controls on the chin shelf (they're flush with the surface so you can't press them by accident) are few in number and well lit. A trackball, nearly identical in size and feel to the one Apple uses in Mighty Mouse, is the star of the show on the shelf. It is not a pointing device per se; there is no mouse cursor. It is akin to the five-way nav buttons (four directions plus click) on traditional phones. This, too, sets T-Mobile G1 apart from iPhone, which uses display touch for all navigation.
Finally, T-Mobile G1 features a removable battery, SIM card and microSD flash memory card. Oddly, it is missing a headphone/headset jack, a common and bizarre design trait common to HTC devices. The USB port, which is also used for charging, has extra pins for audio output. Included earbuds double as stereo earphones and a telephone headset with a lanyard microphone. The earbuds' quality is better than the throwaways typically shipped with phones. HTC sells an accessory pigtail that allows the use of regular phono plugs. This is included with HTC's lower-end Windows Mobile-based Touch Diamond and should be in T-Mobile G1's box as well.
The Android GUI
For most operations, I prefer the Android GUI, which makes its commercial debut in T-Mobile G1, to the GUIs in BlackBerry, Windows Mobile, Symbian, and iPhone. iPhone's inspiration is evident only in G1's flick-to-scroll and long press gestures, both of which are well integrated.
Dedicated menu buttons below the display and on the keyboard pop up unobtrusive, connect-sensitive menu icons in a strip across the bottom of the display. Tapping one of the icons either performs an immediate action specific to the application, such as showing your present GPS location in Maps or pulling up a settings panel that you exit with the back button. The back button also either closes the foreground app or returns to the previously displayed screen, one of Android's few GUI ambiguities.
As you have probably seen by now, program icons are on a slide-out tray rather than cluttering up the home pages. You flick the app tray out and scroll through your apps in a non-hierarchical icon grid. Clicking an icon takes you to that app, or you can flick the tray back in to reveal one of several home screens. You can selectively drag app icons onto the background of any home screen to gather applications by purpose or any criteria you choose.
Android's standard PIM applications (e.g. calendar, contacts) are adequate but uninspiring. However, Android's Java 2 Micro Edition API is well appointed with device-specific features like multiple fonts and rendering styles that make rich application development a breeze, so much so that Android's standard PIM apps can be seen as placeholders. What's more, a built-in Apache Web server, Google Gears, permits the on-device use of client/server Web applications with server-side scripting, making HTML and CGI the quickest route to custom apps.