I have a different take on this... I don't think its just a problem with Costar stabilizers and Cherry switches, but rather more a problem of shoddiness from Filco and the lesser Chinese manufacturers. Seems like Filco's actually have a lot of small problems.
I'm not so sure their reputation for high build quality is exactly deserved. Lets be honest here - they are mass produced in China (or is it Taiwan?) and the quality of construction doesn't seem to be very consistent. I have tried only Filco and WASD boards and to me the WASD was more solid and had less tiny movements in the keys than the Filco. It also produced a more deadened "thud" rather than the hollow ringing of the Filco. WASD's also have a thicker case and pre-greased stabilizers. I think there's a new top dog in town if you want top of the range for Cherry MX switches, I just wish WASD sold a Tenkeyless version. Other people who have tried both WASD and other boards can attest to the fact that the WASD's are a cut above.
When it comes to Cherry MX switches, most people have only tried boards like Das, Leopold, Ducky, Filco, Rosewill, which are all virtually identical in terms of build quality. Yes, the Filco and I believe the Rosewill have plate mounted switches, but they are all mass produced with about the same build quality. To me, a WASD feels like a small step up from these keyboards.
The spacebar really shouldn't be moving on a $150 keyboard. The keypresses should all feel and sound uniform. There should be no resonance or ping. WASD has none of these problems.
At least Filco looks cool?
EDIT: I've done some further reading and it appears that the internals on a WASD are from the same OEM as those on a Filco. The difference in feel is explained not by the internals, but by the quality control measures at the WASD factory for each and every keyboard. Springs are perfectly adjusted, stabilizers are pre-greased, everything is measured, etc. The case material is also thicker. These things all contribute to the more deadened feel of the WASD. By contrast, the Filco doesn't seem to have any of these attention to details and I get the impression that they are simply produced as quickly as possible with lax quality control.
I'm sure a lot of us are quite particular about having the best-built keyboard. That's why Filco's are so popular. We just need to realize that WASD has taken the extra step and deserve to be recognized as basically between Filco and Realforce in terms of quality if we want to be responsible, fully informed consumers. The tendency of Filco owners (I am one) is to explain away the problems with their board... this is understandable because they don't want to believe that they spent top dollar but didn't get a top product. I think this effect is more pronounced on this forum than on a forum about, say, cars, since the people here seem more perfectionist and invested in their hobby. It should be common knowledge here that the 104-key keyboard to get for blue, brown, or black Cherry MX switches is a WASD.