I realize that I run the risk of becoming incredibly tedious about this whole VST3 thing, so I'll post this one bit and leave it alone for now. Pictured above is what happens when I cold-build the supplied sample code (the ubiquitous and omnipresent AGain project, which is the Hello, World of VST, and has been in the SDK since there was an SDK) and attempt to instance it in Cubase 4.
This is amusing on several fronts. They are, in no particular order:
1: The _exact_ same thing happens on OS X. This means that either C4.1 is busted for hosting non-Steinberg VST3s, the API for VST3 is busted, or the AGain project itself is busted.
2: The AGain build verifies 100% in the little application Steinberg provides to test VST3 plugins.
3: Without a working starting project (e.g. AGain), a developer is absolutely unable to build anything. Period. If you don't have a working starting point, you don't know if a problem you're having with your product is due to the host, the API of the SDK, or the plugin itself.
So, well, that's fun. I'm wondering if it's the version of VSTGUI they included that is causing this trouble. I'm also wondering if I care enough to figure it out. Steinberg is really swinging for the fences with this bitch, I'll say that much. Never a dull moment in the plugin development world.