Passed the 350-018 today. Wasn't too too bad. Lot's of stuff covered.
Know ALL the encryption protocols inside and out.
VPN, all types, all platforms.
Switching; STP, Span, Channeling etc
IDS; both the old and new. Sensors and Managers.
CSA, including HIDS
Pix, up to and including 6.3
Routing, nothing crazy, make sure you have a very very strong base on everything.
Unix file structure.
NT structure, permissions, NFTS, Domains.
Basically everything on their published guidelines. The Cisco Press CCIE Security exam guide does a decent job of covering the fundamentals. Whatever you find in there, dig deeper on the web and CCO.
One thing not in their guide lines that should be known, believe it or not, is TR bridging. Had quite a few on that. Fortunately I had some experience with it years ago, but talk about getting thrown into the way back machine, yowsa!
Over all I thought it was a very fair and thorough exam. Lots of topics covered. Nothing too obscure.