Finally got around to demoing this.
First a couple notes:
1. The 64bit VST only loads other 64bit VST's. No big surprise here.
2. It also won't load Sonar specific plugs that are keyed to only run in Sonar, like Vintage Channel.
3. Everything else I tried to load so far worked OK. Some people on the UAD forum have reported some compensation problems in some cases, and Blue Cat suggested stopping/starting playback, switching the plug on/off or stopping/restarting the audio engine should fix this, at least in most cases. I haven't tested for any compensation issues myself.
I tried various things and it worked well. For instance, I tried using a saturation plug and restricting it to a limited frequency range, a narrow band mid/side delay, using a color compressor only on the lows/low-mids, and taking a bass track and leaving the low end dry while running the rest through Amplitube using a slightly overdriven guitar amp that had anemic bass response followed by a chorus - worked beautifully.
I'm not really looking at it as a mastering plug, or to, say, turn
any comp into a multiband comp (how often do you need a multiband comp anyway?). Turning a stereo plug into a mid/side one might be useful on occasion, but it would only work with certain plugs and some of them already do M/S on their own anyway.
But I'm sold on it for my intended uses, and CW just happened to put it even more on sale for me the other day.