I've loved the previous model and put a lot of miles on it. From that experience, this version's balance of softness and stack feels just about ideal. Here are the points I've noticed, from running to daily use.
It's a low-stack shoe, but the small amount of cushion from ZipFoam™ is spot on, ideal for feeling the ground and thinking about form. Personally I think it's good to rotate shoes of different stack heights for easy runs: different thickness and softness spread the load and stimulus across different muscles. I recommend slipping these in between runs in maximal shoes.
Shoes that are too thin get tiring to walk in, but the ST-6 has enough cushion to work for commuting and standing all day in the shop. As a walking shoe it balances a barefoot feel with low fatigue very well.
It's handy for the gym and for carrying: it slips into a bag easily, so it's great for a run while out and about or the gym after work.
On sizing: like the previous model, the heel hold is good. The arch is deliberately snug, so the fit is very secure, but if you want more room or dislike a tight midfoot, consider going up half a size.
