Ok I got the firmware.zip and played the zn games on it too.
I wish I hadn't

....... 30 fps and my machine is a 900mhz with a 32mb video card and 500 and some odd megs of ram.
Now the namco games are a totally different story, they run at about 130 fps if I turn the limiter off, but of course you have to take into consideration that the sound hasn't been emulated on those games yet.
Belmont stated on the site that impact and s11 are now obsolete and no longer supported....
My opinion... ditch s11 since zinc is basically the same as it with better framerates, but impact is far superior in terms of speed right now, so hold onto it.
They also stated that it could be several months before redefinable keys are added. Isn't that kinda like releasing a car that only makes left turns.

If they keep up development this will be the 3d equivelent of mame (as I predicted months ago) but if they don't get the fundamentals like a higher framerate and redefinable keys it may become lost.