For those looking for the answer to this, as i am, hopefully a dev can explain for us...whats the difference between the ROMs on the DX and the CUSTOM ROMs on the D1?
The original Droid is the only Motorola Android phone that does not have a locked bootloader, allowing you to install a custom recovery and a custom kernel. Those two things allow you to install just about any build of Android you want that is independent from Motorola's software.
The Droid X, however, has a locked bootloader that only allows for signed, Motorola-approved software. That means you're stuck with their kernel. Even though it is open-sourced, a developer isn't able to recompile that kernel with new features and bug fixes and install it on his own device.
That said, you are still able to modify 100% of the user-space, that is everything outside the kernel. So our roms only affect everything in the /system/ folder. We can get very close to having a stock Android experience, but it will always be dependent on the underlying Moto kernel behind it.