Lets look at this realistically - the BMW autoboxes are much better than the basic type auto gearbox in the Holden. These are performance orientated executive cars and have more complex and better performing and feeling auto gearboxes. They aren't as responsive as say a full on Sports or fast executive car like say a similar period AMG or Audi auto, but not all that far off.
In short, they're an excellent gearbox for what they are, kickdown responsiveness is fine and the steptronic gives you that added dimension of tipping the gears up/down. If you look through all the BMW forums, there's hardly any posts complaining about the gearbox responsiveness.
Keep in mind the maintenence on these cars can be high and when things do go wrong you will need X% more funds to put it right again.