I do not have a Wally scope, though I do have a microscope. For me, it is a tool to get close as well as see where the final by ear adjustment leaves the angles. Cartridges of the same type (model number) from the same manufacture can have differences, especially in the alignment of the diamond on the cantilever. It also helps to observe any changes over life of the cartridge.
So I bought a WallyScope...
It's a very nice microscope and the software that comes with it, while I assume off-the-shelf, is excellent.
But here's the thing. At the end of the day, you are still basically eyeballing your VTA setup, and the instructions for the WallyScope have you do two separate observations to reach your conclusion. The first is the angle by which your stylus hangs off the cantilever, and the second is the angle of the cantilever versus the record surface.
I understand why this is done. It's so that you can measure with the record moving to get the dynamic rake angle instead of static, so that's one error that the method corrects for. But at the cost of introducing the compounding observational errors by taking two measurements and then combining them to calculate your angle.
I was very patient with this process. I spent many hours over several days. I even dismounted the scope from its frame because I found a better way to line it up for taking measurements.
And after all of that, I adjusted VTA by listening. Which achieved better sound. This came to me as a revelation, although it shouldn't have.
I don't regret the purchase, but it's a lesson that we can and should trust our ears.