The evolution of self checkout systems

It's interesting looking at how the whole self checkout system at supermarkets has evolved since its recent introduction (at least here in Oz).
The early systems were fairly simple.
Click to start.  Swipe things through.  Once you filled a bag, press New Bag, wait, then remove your filled bag onto the ground and continue swiping.  Get to the end and select one of several options for payment.
Then there were the systems that allowed you to remove the bag when it was full without prior notification.  Once it was removed, it asked you to confirm that you'd just removed the bag.
Now that confirmation of bag removal has gone, which, together with no need to press Start before scanning, leaves us with a smoother workflow.
This is the sort of change that could have been in the system from day one.

However, there are a few other aspects that have changed at the local, and I'm unsure as to whether they could have been as effectively rolled out on introduction.
In some ways, they seem to make the system a little more complex in order to offer more features / flexibility.
I mean, it seems intuitive enough now.  But is that just because I (and other shoppers) have had some time to become acclimatised to the system?  Always difficult to tell when you're trying to recall what things were like the first few times you encountered them.

Now we have the option of cash out or shopping to begin with, reintroducing that top level menu prior to swiping.
End level menus have changed upon completion of shopping.  I think this gives a fast and flexible workflow, but I also think it's introduced a couple of extra menu levels that weren't there before.

Certainly I'm liking where self serve checkouts have gotten to and where they are going, but it has given me some pause as to whether you can just roll out the wonderful end system on introduction, rather than going through years of modification to get there.  It's not a technical issue, it's a people process issue.
Maybe you can just introduce ultimate system on day zero.  But maybe you can't, quite.