I find it interesting that other than Smitty and myself none of the other responders to the initial post have owned a ZB.
While the ZB was manufactured in Germany it is made up from the GM parts box. It is very different beast from most European cars. The LGX 3.6 V6 engine (a development of the LFX in the VE/VF) is made in the US, as is the LTG 2.0 turbo4 and the 9 speed transmission. The chassis platform was developed by GM North America, Opel and Saab.
The LTG turbo 4 engine is fitted to the likes of the Chev Camaro, Impala, Malibu, Traverse, Terrain, Equinox, Cadillac CTS and ATS, Buick Regal. It has a good reputation in the US. The LFX V6 engine is fitted to a just as wide a range of vehicles
I have had Commodores right the way through from the original VB SL, then VC SL , VL Calais, VY S, and now the ZB. My wife has a VE Z series S. They have all been good cars. Without a doubt the ZB is the best equipped and best driving handling Commodore of the them all. So far it's reliability at over 90,000 km is as good as the other Commodores I have owned.
For some reason the ZB attracts a lot of knockers in Australia. A bit like the VB when it was released back in 1979. The reactions on the Buick Regal owners site to the Buick Regal, the US variant of the ZB, are like chalk and cheese to the reactions I see on here.
One other thing that is startlingly obvious is the number of ZB's on the road in Australia compared to New Zealand. I regularly travel to Australia and the ratio of ZB's I see in Australia is probably greater than a 20 to 1 less than are on New Zealand roads. The VE/VF was the top selling large car in New Zealand and the ZB continued that tradition, I rather doubt the same happened in Australia.