Mach3 takes liberties with the Windows OS. Microsoft designed Windows to be an absolute control freak and it will not release that control unless you massage it in just the right way. As mentioned before, much more expensive controllers use independent hardware to achieve smooth motion and a feature rich environment in Windows. Mach3 is all software, baby! No expensive hardware at all. To be honest, as far as I know Mach3 is the ONLY exclusively software based motion controller operating on the Windows platform. Making it work at all was in itself a great feat.
If you told him a Ford Focus was just as good as a Ferarri, would he look at you funny then. 'Cause it's pretty much the same thing.
Actually, I see it more like a Ford Mustang vs an F1, but with the Mustang, at a fraction of the price, they also throw in a complete workshop to tune it up as you see fit. However, you still need to know or learn how to use the tools to tweak and tune the performance and make new parts to produce a car that is truly drool worthy. In Mach3, the same is true - you get a decent base model and if you're willing to learn (or pay someone) you can have one slick machine. That being said, don't expect it to outperform the F1 on the track, but you can still get way more functionality and enjoyment out of the Mustang.
Feedhold function in Mach3 stops at the next convenient and safe spot to guarantee that you can resume without problems/lost steps/sync issues. Perhaps it could be better with the developers spending more time on it, but I guess it is what it is. Likely this was the easiest way to make it work within Windows.
I don't think people were trying to beat on you, but instead trying to impress on you that Mach3 was designed for the hobbyist - it just so happens that it's good enough to be used in production roles like in my shop - and I wouldn't change to a commercial controller at this point. With Mach3, where there's a will there's a way. With commercial controllers you are locked into the functionality that the developers decided you need. To each his own.
Please don't hesitate to ask more questions about the limitations and any quirks you find - many people have had quirks that are not normal and can be fixed, but if the experts here are telling you it's normal, please resist the urge to compare Mach3 to a commercial controller, as Mach was not designed to be a commercial controller replacement.