Oil leaks are pretty much standard on the old ecotec 6, and on the previous six cyl for the VN to VR. Power steering leaks are extremely common, as are the pumps failing. Ever commodore I have ever looked at has a leaking or weeping rear main seal, including mine and my parents. My rear main isn't too bad, it just weeps a bit, but the parents has been done twice under warranty, first time was when the car was six months old, and it still leaks now, even dripping on the driveway. Its certainly not worth repairing the rear main due to the cost of the job, but aslong as you degrease it often, its generally ok.
Transmission gaskets also leak, but that can be easily fixed with a trans service. I haven't had any problems with my diff leaking, except for the diff breather pipe, which did leak at one stage.
The other common leak is the rocker cover gaskets, mine aren't too bad, but the parent's VS leaks pretty badly.... don't know why, it has heaps less km than mine...
I guess that with the age of the VR and VS now, a lot of seals will be perishing or wearing out, so you have to expect do some replacing along the way...