The main obstacle is Willunga Hill, which you may remember from when Thor Hushovd won the Worlds. It's not a mountain, but it may be difficult enough to keep the sprinters from winning the race. If Gilbert were racing it's the kind of finish he'd kill on. They are giving out time bonuses on the flat stages, though, so it should be interesting to see if the sprinters can hang on or if the hill climbers can gain enough time to take the GC.
Your best bet may be a guy like Boasson Hagen who can sprint and climb.