This is the sixth tamper that I've used in my home espresso experience, and the best! First, I love the fact that you can adjust its height, using the supplied washers. I have fairly large hands, and this is the first tamper I've tried that I can get to fit perfectly. Second, being 58.55 mm in diameter, it certainly gives the tightest fit in the baskets I have (VST and Decent), and that makes a difference. There's hardly any coffee left on the basket walls after tamping, and when knocking out the puck, it's apparent that the water gets to more of the puck edge during extraction than with narrower tampers. It's not a huge difference, but it's noticeable. On the whole, I get slightly more even extractions than with other tampers.
As great as the Pullman BigStep is, it's not perfect, for me. The top of the base is made of rubber, which is great for relieving pressure on the fingers, but does attract coffee dust, which I find annoying. Also, the Pullman is a little light for my taste. In that regard, I prefer the Pesado tamper, for example, which is almost double the weight, feels much nicer to hold, and requires less force when tamping. Finally, I don't particularly care for how the Pullman looks, especially the writing on its base, but that's really picking nits. On the whole, I still prefer the Pullman over any other tamper I've used, because of its functional advantages.
I should also comment on the price of the Pullman BigStep. It's certainly the most expensive tamper I've used, and the price is a little hard to justify, given that it's basically just a chunk of metal, even if one that's made very precisely. Also, compared to something like a cheap Rhinoware 58.4 tamper, it's not going to massively change the quality of your shot. The advantages it offers are nothing like the difference between a cheap grinder and an expensive one. But if you care to chase perfection in the espresso game, then I think there's no substitute among traditional tampers.