First of all, the CoS isn't what it used to be. Things have just changed since LaVey died. I've noticed a strong elitist attitude from a lot of CoS members and I'm not sure why really. LaVey made it pretty clear that he chose Satanism because it got people's attention and we all know that even negative publicity is good. This isn't really a secret. I was a LaVeyan Satanist for several years and there are a lot of ideas in the Satanic Bible that I still agree with. I don't have a problem with modern Satanism in general because it does use Satan as an archetype. However, I have a big problem with any Satanist (or any person really) who claims their way to do things is the only way.
The reason I left the CoS is because after 6 years of being a modern Satanist, I realized two things. The first and most important thing is that I identify more closely with Lucifer than Satan. The second important discovery that I made was that I'm not an atheist. I just can't believe that there is nothing. I felt that these were important issues...important enough that I sought out something knew and actually, I didn't find anything. I began, at that point, creating my own path. Trust me when I say this is quite time consuming and takes a lot of study. I decided for myself that I was a Luciferian (I made the word up, actually). It wasn't until 2 years later that I finally ran into other people who had done the same thing I had done. They created their own Luciferian path. I have found that most people who claim the Luciferian name have done it on their own and that is why we are a pretty disconnected group.
By being a spiritual Satanist, you are at least to some extent, having to create your own path. You have to create your own bond with Satan and that is a very personal thing. Nobody else has any right to tell you that you are not a Satanist. You and Satan know better. That is all that is truly important.