HTC's page on the G1 is now posted and, boy oh boy, is it detailed. Check it out. Details on top of details:
256MB ROM / 192MB RAM (The ROM is for Storage, the RAM is for running programs)
4.60 in x 2.16 in x 0.62 in
3.2 inch 320 x 480 Touchscreen
Radio Bands: Quad Edge, on the US the bands are 1700/2100, in Europe it's 2100. In other words, if you do manage to unlock it, it won't do 3G on AT&T, only on T-Mobile.
Bluetooth 2.0, WiFi, HTCs Funny ExtUSB connector for Headphones. This is a bummer, no 3.5 mm headset jack.
3.2 megapixel camera
1150 mAh battery, sort of small, but supports 350 minutes of talk time
MicroSD for expansion
Accelerometer as a motion sensor and "digital compass"