I have a ViewSonic E70fb which I need to test with again. I was using an older adapter (also ViewSonic), which led to a green tinge over the picture.
Using the Apple-branded DA-15—DB-15 adapter they included with B&W PowerMac G3s got me nothing as well. The E70fb covers a vast array of resolutions and refresh rates, so it's a tad mind-boggling why it wouldn't work...
I thought about grabbing one of those later VS-branded adapters or even the switchless NEC adapter.
I tried to get my Sony (Vaio themed) flat panel to work—which it does with every PPC Mac I've got, thanks to a Radius Pivot cable I was given by a member—but doesn't work un-adapted. It's a shame, too, because it supports a 1:1 pixel mode.
I guess my go-to for these has always been Apple CRTs... I have an AppleColor 13" and a Multiple Sync 20" which are both problem-free, as expected. Well, the problems with the 20" are plastics related, but thats got nothing to do with electronics : P