The first Piko starter set (38100-Union Pacific) had curious issues for sure and this one was what G-Scalers would consider highly mass-produced, as the first 1,000 sets arrived in San Diego before the manager in America got to see what they did. Unlike most manufacturers, Piko fixed the problem. Any consumer who called in, for 7 years, got the parts they needed if they asked. (I have one of the locos, and still run it using the updated motor box.) That was the first North American product, and was made over 10 years ago.
The main issue with the set (aside from producing the wrong yellow on the caboose) was someone in production - not the American folks - decided that they wanted these to be the toughest garden trains available. So they decided to powder coat the wheels. Now, powder coating is quite strong... but it is not the best for electrical contact on brass track. It works ok, but was not a smart move. Some folks wrote Piko off because of that mistake a decade ago.
I believe the loco shape and tooling is the still the same. I was told the owner wanted fewer details and parts to apply on the first product because of worry over how they would sell. Future models have gotten more and more details. (The Camelbacks look pretty good! I have a 25-Tonner on order which is expected in mid-November.)
Piko went from that, umm... interesting beginning, to what they are today. Most manufacturers, if they produce much of anything, have lowered standards and are choosing to do so in order to save a few bucks on their costs, while raising the price to us. Piko has continually improved things so that they can honestly say they have the best brass track on the market and many other things. (They had some emails that went out explaining how they can say that... They were VERY informative if you know what else is on the market!) The price for their products is very reasonable when you consider what others are charging for similar items.
Piko is bringing new products to market when every other G manufacturer seems to be faltering or dying. (Or that is what it seems like.) I have heard many people say Piko is the new LGB in that Piko has taken the place of LGB in their minds... based on design and quality. I have not met an honest person who can say that Marklin/LGB product is the same as it was even 10 years ago. (It is NOT.) So maybe they have something secret going on in Germany at Piko, but either way they have shown to be an upstanding company.
(I happen to own a good amount of Piko stuff and have never had any problem.)