I've used Atmosphere for years, and when I heard about Omnisphere, I jumped on it as soon as it was released.
While Omnisphere has a lot of "single key" patches that play themselves, that's the tip of the iceberg of its capabilities. It does have a wide variety of simpler, cleaner sounds that can be used for sound design. It also allows you to build complex patches from multiple sources. Each patch can consist of eight soundsources, be it sample-based or generated sounds. I doubt anyone would want eight soundsources in one patch, but the fact that the option is there is nice.
It's a damn powerful tool, and can be as simple or complicated as you want it to be... you just need to dig down to find all the extra control it offers. It's a shame that they promote it the way they do, because it's seen more as a toy instead of a serious tool. FL Studio has the same problem, but that's a conversation for another day.
For me, while I do dig down once in a while, I like the simplicity of it. I'm more interested in making music vs sound design, and it is a great tool for making music. If you do plan on using it, just don't choose the easy
patches and your music won't suffer from "I know that patch" syndrome. And if you do use the easy patches, beat the crap out of it first and make it your own.