I think Rudd's biggest difficulty is overcoming Gillard who in my opinion is not electable as deputy PM (way too far left). The Liberal party will go after her at the election.
Kevin Rudd seems to have some good ideas and seems to present himself very well. I think Howard is setting him up somewhat over the global warming issue and also over Iraq.
The one thing to keep in mind is that whoever gets in, the IR laws will stay and at the most will be fiddled around the edges. Labor will miraculously discover that they can't be repealed if they win office just the same as they backed away from their GST pledge.
Cheers,
Reaper