Bajan Blue
I do think originally it was a good idea, poorly executed unfortunately and now everything else plug in wise has improved so much, it has possibly missed its time.
Nigel
While I can agree with the impression that Nebula's success has been unfortunately diminished by a somewhat amateurish promotion/marketing/support regime, I don't agree that it has yet missed its time -- if anything, it's a technology ahead of its time. It does require a fair bit of DAW horsepower, although this is less of an issue than it once was -- I can run a couple dozen instances on my i7 just fine using the "reverb" version of the plugin (an example of one of the counterintuitive Nebula quirks). But as for sonic performance, there are Nebula libraries that to my ears beat any regular plugin available. A common Nebula characteristic is the sense that you're using something better than a plugin, something closer to hardware, with smooth frequency response, a sense of depth and weight, and without the usual digital artifacts. The idea is to "sample" a real piece of hardware using a very labor-intensive process to capture all its flavor and store that into impulse files (which can be very large). It's much more than simple convolution, but the basic concept is similar. Not that I'm an expert or anything. But the results to me are almost always impressive.
To get an idea of what's possible, you can download some free VST plugins that use Nebula's technology from CDSoundMaster -- they run just as regular plugins, no Nebula engine required:
http://cdsoundmaster.com/site/cds-software-online/demos.html. Be sure to check out the Neve 1084 mid-band EQ, for one. Have fun!
Cheers,
Eddie