It's been a rocky road with me and Nebula. After years of passionate endorsement from other users, my jury is still out on this thing. I understand the developer is breaking new ground, but I have trouble regarding Nebula as anything other than an experiment in progress.
First off, the interface - despite its cool, retro look - is confusing, and worse, extremely sluggish, and tough to make precise settings. There is also a delay when changing banks and presets; just one of those things that ads up to a tedious experience. Lots of silly names don't help the user understand what model is what, but I understand this is a limitation in a world shackled with intellectual property, but most of them are simply indecipherable.
That being said, it's nice that the user has full control over the presets (programs), and can download and install programs at will. Although the sluggish, convoluted Nebula ethos is extended to the website, where it's very confusing to tell what section you're in, which one you should be in or where you get your standard presets from. Perhaps I haven't spent enough time on these sites, and the newer site is a vast improvement on the labyrinthian, punishing old site, so maybe it's just me. But I find it hard to tell what program or application is which, or which is an update. Oh well.
So sound-wise, this is where the big payoff should be, right? I personally think the user interface puts me off so much that maybe it colours my opinion, but I've never heard anything that blows me away. Some of the EQs definitely sound nice, if I can find a program that does what I want, but I've found the compressors to be very strange sounding; more like transient designers than the sacred equipment they're supposed to be exact clones of. Again, maybe I've just installed the wrong "programs", but I would point out that this doesn't really happen with any other effect I own, and is counterproductive to mixing.
Time-based effects don't fare much better, with choruses sounding like a single sine wave carving through your track. I just don't think this technology is ready, at this point.
And the latency is outrageous. I'm very used to high latencies, I'm not that picky, but adding a couple of these to a mix will make my DAW feel terribly unresponsive, and CPU builds up quickly. I just don't hear the crucial reward of stunning sound I'm supposed to hear for such a deadly performance hit.
Support is very good, the developer is a good guy and clearly believes in the product and wants to help, clearly doing his best. I always enjoy dealing with him.
I hate to be hard on a nice, independent developer, but this product just hasn't clicked with me. I've bought and stuck with it for the promise of the future, and we'll see where it goes. For now, it sits unused on my hard drive. Unfortunately, in the meantime, virtual analog technology is getting better and better, so I would like to see some serious optimizations in this product before I take another stab at it.