Atmosphere (and the other Spectrasonics stuff) isn’t really a Synthesizer because every preset is based on large samples. It is a kind of advanced player for embedded samples. There are nice sounds but it is not usable to create new patches. Apart from Atmosphere, Best Service and Native Instruments distribute lots of alternatives with acoustic and digital instruments embedded into plugins.
i love atmosphere…it has some really beautiful samples and is great for getting away from the sometimes generic/formulaic pad sounds produced by your standard subtractive synths…. + if you keep bouncing and layering wavs produced by atmosphere together, you can produce some incredibly rich and detailed soundscapes… shame about the price is all…ouch!