Somehow, Levelup.cn got access to a PSP Go, which they proceeded to disassemble for our amusement. You can browse through the thirteen-page gallery (!) and really look for the UMD drive that must be hidden in there somewhere. You can also see the internal memory and the battery, which is now non-removable (and, Sony hopes, non-moddable as well).
Perhaps of greatest interest to old-school PSP owners is that the D-pad and buttons are very clearly separated from the screen hardware by quite some distance. There shouldn't be any square button issues this time!