Couldn't agree more ...

My chosen field is UNIX Systems Design and Management. Given 15 years experience, and several large scale
environments I have worked in; it is relatively easy to focus a lot of time and energy on UNIX/Linux security.

Sure, there is some bleed over into other areas like network, web, and physical security. For the most part
though I look to folks that specialize in those fields to implement a secure design, rather than trying to do
it all myself.

If you choose OS security management, beware that often times what would be the most secure just isn't going
to be possible. You manage systems because the company and your users need them for some business purpose.
If the business needs and the security needs are in conflict guess who loses. I don't know your situation, but you
will likely find that your first security job will be at a company full of old, unpatched systems that absolutely must
stay that way for some support reason or another. That's what makes 'real' security far more challenging than
the theoretical scenarios found in books and suggested in articles on securityfocus.com.

Just remember this and you'll be fine. A lot of security is keeping one eye on the big picture, and the other eye on anything that looks out of place.