All the new Power Functions goodies from the 9398 Crawler nicely reviewed in this video by Sariel, it helps a lot to figure what possibilities these new elements have.
Also there's another interesting review by LasseDeleuran with nice speeds comparative.
The new receiver, the IR V2 is a good new, now it seems that we can ad motors to the receiver without break it like in the first version of it.
The servo is quite interesting, like nxt motors but controlled with both remote controllers (classic PF and trains PF) and with the battery box, nice for steering (of course) and other devices like valves, GBC modules, control pneumatic stuff, technic "sculptures", Victorian machines...
And the "L" motor seems stronger than the "M" but not as destructive as the XL, known as the "pin bender"
Can't wait to have one 9398 crawler set in my hands.