i just physically picked up a new Glock Gen 4 today. it does not appear to be Laser Max compatible as it has a similar recoil spring system to the mini-Glocks.
it has different stippling than the RTF and the Gen 3. the slides are marked "Gen 4." has a lower profile magazine release which can be switched to the other side for lefties. magazines are slightly different in the fact that the cutout where the mag seats into the magazine catch is metal lined.
of course there are the two additional backstraps. as it has been explained to me the original backstrap is the same as the short frame (SF), the medium backstrap is the standard grip on the Gen 2/3 Glock 17/22, and the fat backstrap is the same as the Glock 20/21.
from my understanding these pistols are only currently being made for the full size .40.