I think Giteau has been coming into form for the brumbies, but as Gnostic alluded most of his brilliance are shown when he is a second receiver.
I think Giteau's best asset is his footwork so to get the best out of him you really have to play him at 12. Same situation with O'Connor really. Gits and O'Connor have decent skills but these should be the bare minimum for an international player. Just because JOC (James O'Connor) and Gits can pass doesn't mean they are best suited for 10. Every player in the backline should be able to pass like them. JOC (James O'Connor) does look he could be better, and probably already is, than Giteau. However Q's surely remain over his defence. Giteau's defence is topclass even if it isn't at the same standard as barne's tackling, which is superhuman.
I say give JOC (James O'Connor) a chance for the first couple of trinations, but if there is a suggestion that he could be flaky in defence then go with Giteau for the RWC. Whilst JOC (James O'Connor) might cause Sonny bill a couple of problems, I'm more concerned about the problems SBW will cause JOC (James O'Connor) on attack.