While maybe a bit better than the other alternatives, I think that Filco was mostly a fad here on geekhack. At the time there weren't many mechanical keyboards, just the steelseries and razer ones. This made the Filco something a bit more exotic since it wasn't from a mainstream US company. It also helps that it offered more switch options, didn't have gimmicky features and didn't have some of the problems that razer keyboards had. So while it was a good keyboard, it's not really something to get super excited about anymore.
Now that some people are getting some "Korean customs" that's the new fad. The CM Storm Quickfire Rapid provides very good bang for the buck. With the Filco, you're paying twice the amount for an increase in quality that a very large majority of people will not even notice, if it's even there to be noticed at all.
There are some horror stories about Rosewills that should have failed QA, but a properly functioning Rosewill is probably a fine keyboard.
In general, a lot of the stuff that becomes popular on geekhack is popular because it is rare, hard to get, expensive, or good looking rather than because it's the best quality. That's not to say say that these can't coincide, but when you read reviews that people write about them, it's mostly like "it feels solid" and "nice looking construction." There's usually not much about them that makes them stand apart in terms of functionality. I also want to say that for people who love keyboards so much and probably use them a lot, there's very little love for ergonomic keyboards.
But in general this is how hobbies work. If there weren't new fads to hop between, then there'd be little reason to stick with the hobby as there'd be nothing to talk about or collect.
I don't have a Korean custom of my own, but just to show that I'm not completely biased here's a quote from a rather reputable member here who does have experience with them:
I ship it out to the happy owner. I've done 2 or 3 Cheats, built or modified 8 or so KMACs, couple of KMinis, MXminis, LZ boards...
None of them really caught my eye. I have bpiphany's controller for my Filcos so I have everything I need in terms of control over what my board can do.