Hi Lee,
That looks like a nice piece of kit, albeit somewhat over specified.
I have been using a Wild Heergrugg M5 now for about 4 years courtesy of an amazing car boot sale find and I wouldn't be without it. For me the advantages are a much better view of proceedings (obviously) and a much more comfortable working position as it allows a more upright seating stance, not so hunched up. Proper stereo is important for judging distance.
My setup gives me 6, 12, 25, & 50 times mag as standard but it came with an attachment which allows control over depth of focus and increases mag by a factor of 1.25. I use 6 & 12 for most stuff, 25 for hair spring work, and 50 for inspecting jewels and pivots. More than that is of little or no use. One very important factor is working distance (how much room between the watch and the object lens when in focus) as you have to be able to get your tools in there. Mine varies from 12-15cm if I remember rightly which is fine. The one you're looking at states 10cm but that may well change with different magnification, and if that is the max then it's worth asking exactly how it changes as this may well restrict its usefulness. One other word of warning; cleanliness takes on a whole new meaning under 50x mag. Be prepared to get a bit obsessive about it (not a bad thing in a watchmaker).
It's quite a lot of money to shell out though so worth asking about the working distance. And if restricting the mag to 50 - 75x saves money then that's worth considering as you won't miss the higher mag in practice.
Have fun.