I've had a Menzi Muck A91C for three years now and have been on it full time.
Great machine, John Deere Engine, rexroth hydraulics, nothing really to go majorly wrong, service it every 250hrs, had a few electrical issues but nothing more major than rubbed through wires.
Unless you've had walking excavator operating experience I wouldn't be investing in a new one, purely for the fact that the machine will get knocked about no matter how good an operator you think you are, they are the type of machine that takes a lot of learning before you can safely put them where the spec sheet says they can go.
The hardest part I've found in Australia is that there is no market for them other than the one you yourself create.
I've put heaps of time markeitng the machine and it has taken two and a half years to get it to the stage of plenty of work in front of me for good return on investment.
Hope this helps
Chris