After using Neb for a week or so (and just loving the sound), I think the category thing is not such a problem (unless there is a limit on the number of files that Nebula3 pro can read from a directory in Mac AU).
More important to work on is overall stability in the AU version. In DP7.2.2, Nebula works but is quite crashy, whether or not CUDA mode is engaged. Opening a new instance, opening the GUI, dragging from one insert slot to another, loading a new patch: any of these might or might not cause a random crash. This needs improvement first and foremost.
It's not unusable, but it's crashier than a pro-level plug should ultimately be. I'm sure you're working on it.
@biomuse: could repeat those tests using an empty song? What about the memory usage in your actual project?
I've found that Neb is quite stable in other sessions, and I believe the difference to have been either:
1) More VI's running in the first session vs. mostly or only audio + fx in the others. (Is it possible that Neb has some trouble entering/exiting DP7's pre-gen queue with VIs running? Or that there could be a specific VI incompatibility with Neb?) RAM partition was just over 2.5Gb for the troublesome session, so that probably wasn't it.
2) Since then, I have raised DSPbuffer to 2048 (non-reverb). Is this recommended in general?
I will keep an eye out for any specific incompatibilities I can identify, but this is probably not a Nebula-only issue.
UPDATE: OK there is a recurring problem, with no memory ceiling issues and no VIs running: sometimes, instantiating a new Nebula somehow "corrupts" the signal chain, such that I need to disable each fx insert in order to get any signal back. The plug the disabling of which restores signal is not always Nebula (!!?), but it's always the instantiation of a Nebula, the second or higher instance, which causes the silencing in the first place. Strange and annoying. Possibly incompatibility with another plug.
UPDATE2: What solves this problem is simply reloading the patch in the offending instance of Nebula after identifying it.
So it may be that in DP, multiple instances of Neb have an intermittent issue with patch loading and a new instance, where the new instantiation corrupts a previously loaded patch in an earlier instance. Easy to work around and not too common, but a reproducible bug.
The presence of other fx plugs may matter. Other plugs being used in the sessions include: bx_cleansweep, elysia mpressor and alpha master, Waves de-esser, MOTU MasterWorks EQ (MAS), AUMultiband, 2CAudio Aether 1.5. Pre-gen mode is on by default.