3.0 is the full operating system, with low level libraries, new kernel, memory management, services, etc, etc, etc...
Originally Posted by sketch42
3.0 may have even bigger memory requirements than 2.1, so, it's unlikely that 3.x will run on 256Mb devices, but may run on 512Mb ones (from Pre+ to Veer). The problem with the Pre+ is that is not supported anymore and probably there will be no compatible kernel.
Pre2 and Veer are said to support 3.0. We can only hope