Spectrasonics isolated the problem for the first time a couple of months ago, they'd not been able to repro until then but they finally got themselves a misbehaving rig which enabled them to work on fix. I tested some betas for them as a sufferer, and now it's out for all. There's an old thread on KVR of those who have had the problem, and so far everyone is ecstatic - it's a night and day difference.
Spectrasonics did tell me that they were working on further improvements, but maybe the release version actualy rolls them in too because it's so good.
Ironically I've just switched to a new rig so I can't really test any more, but performance is absolutely on a par with the silicon Mac, maybe even better.
Here's the full changelog:
Update available on the website and in-app via their slick updater system.Adds support for VST2 to VST3 replacement
Fixes issue on macOS where the instrument repeatedly asked the user to authorize
Fixes issue in Chorus Echo effect where tempo changes could create clicking artifacts
Fixes issue where the plugin could crash when sent long SysEx MIDI messages
Fixes issue where Multi load actions could fail when using MIDI events to load Multis into multiple plugin instances at once
Fixes issue where the Unison & Harmonia phase controls disappeared when GUI collapsed
Fixes issue where the VST2 or AAX plugins could crash when a DAW is loading the saved plugin state with the GUI closed
Fixes VST2 crash that could occur when plugin was placed within sub- folders that contained a space character
Fixes issue where the plugin could receive corrupted host automation values from Logic Pro when modifying automation assignments in the plugin
VST3 only: Fixes bug where MIDI clips generated by the Arpeggiator's MIDI Capture feature played back at half speed in the Host.
Windows only: Fixes GUI performance issues