Having managed to get my plugin to run in the Juce plugin host as a VST3 at last (still not quite worked out specifically how I messed that one up), I'm now running into a couple of issues with my functionality.
My plugin loads a configuration after startup, so the parameter definitions it initially gives to the host have dummy values. Once the real parameter names etc. are in place, I call updateHostDisplay() and in the VST2 version, the new names are correctly picked up by the host. In the VST3 version, however, this same technique doesn't seem to work, as I still see the dummy parameter names when I "Show All Parameters" from the plugin host.
I've tried to debug exactly what's going on and there's definitely some big differences in the code path taken by the VST2 and VST3 plugins from the updateHostDisplay() call. There doesn't seem to be any code that I can see that makes calls to getParameter after the initial setupParameters(), so I wonder whether this just isn't implemented yet?