Nexus S will ship with support for "fastboot oem unlock", allowing for reflashing of the system software "out of the box", like Nexus One.

Something that may interest this community is that the NDK (native development kit) for Gingerbread now supports native apps (intended to simplify mobile gaming ports, etc) -- providing: libc, libm, libz, opengl|ES, opensl|ES, input/events/sensors, app lifecycle management, etc. JNI is available to access various higher level Android APIs as necessary.

2.3 (platform 9) SDK: http://developer.android.com/sdk/android-2.3.html
2.3 (revision 5) NDK: http://developer.android.com/sdk/ndk/index.html

Platform sources should ship at or shortly after commercial launch of Nexus S.
Kernel git repository (2.6.35 + android + s5pc111/nexus-s) will be available at or shortly before launch.

Enjoy!

Use adb install to install apps via usb (including third party app stores).

If it were possible to ship the N1 with the necessary collection of power amps and suitable antenna design *without* impacting the form factor (making the device thicker) to support both AT&T and TMO and the standard european/world GSM/UMTS bands all in one device, we would have shipped it that way.