I have had my Z2 DX-350 for a few days now. The build quality is really, really good as the previous poster stated.
It does not seem very forgiving to differing battery sizes. It is not a double-adjust so I have had problems with flat-top batteries not fitting well.
I'm not sure if I care for the switch. Compared to the GUS and PAPS it seems clicky-clunky. The switch is well-built, I'm just not sure if I like the action/throw. Mine almost seems to 'grind' when I depress it. I didn't see any way to lock the switch but it requires a fair amount of force so I don't think it will fire just by setting it down.
Overall a nice unit. I like the modular nature of the Z2 line and can't wait to try the Carto
tank, but if I was looking for a straight 18350 mechanical (at this build quality/price) I would probably spend a few $$ more and go with a GUS core or GP PAPS.