I personally think the serious problems are few, so I'll start there. Many of these, while I call them serious, aren't unique to Z and are similarly acceptable within reason. As with any hobby, the choice of scale in model railroading involves a balance of personal tastes and various tradeoffs.

First, and it impacts a lot of aspects, are the laws of physics.

While a lot can be miniaturized, there are parts which would be too delicate if reduced to 1/220 size.

For instance coupler mechanisms which can be realistic in HO are difficult in Z. Yes they are available, but the hobby has not standardized on them and conversion is difficult on some models. Converted (or even stock supplied as with some manufacturers) these couplers increase the problems with turn radius and car overhang. And you can pretty much forget miniaturized prototypical European coupler designs. Other details like pipes, ladders and grabirons end up raised ridges or oversized. Catenary overhead wires must be of huge dimension or they couldn’t stand the pressure of the pantograph.

Lettering and the rest of the painted details are much more limited in what can be reduced in this scale without being a nonspecific blur. Think of one inch lettering or stripe as a detail of 1/220”. That’s less than .005”. Control paint lines from bleeding with even less spacing between them?

Further laws of physics, the “impact” (yes, a pun) of gravity. While the smaller scale rolling stock and engines are of less weight than their larger scale versions, the distance from table top to floor is the same (if not higher as we might like to bring these jewels closer to eye level). Those parts which have been successfully reduced in scale are prone to suffer greatly from this and other forces (like the tight grip of the unaware “observer”). The look – don’t touch motto perhaps more significant in this scale.

YES this is common to other scales as well. But the greater the miniaturization, the more pronounced the problem. Sometimes it’s a functional influence. Other times it’s only in the visual perception.

The other problem is cost. The respective price of these models seem to vary inversely with the scale change. But this might be acceptable considering the degree to which the size reduced detailing problem is overcome. The truth is that despite the problems, these models have remarkable if not miraculously fine detailing.

And a final issue is the limited availability of choice. While over time the manufacturers have produced a great many variations of train sets, locomotives and individual freight and passenger cars, this scale is still much younger and is much less popular than the larger scales and many of the items are out of production and difficult to find. Many were of limited production runs to begin with. This factor contributes to the models’ already higher selling prices.

But in my opinion, which is shared by an increasing number of hobbyists, all this makes the Z model all the more attractive and endearing. Look at some of the close-ups of the cars and you’ll see.