Additional Security in the Linux Kernel?

nyx asks: "Recently, I was looking for some way to improve security on my linux boxes. I found few linux patches like grsecurity, LIDS (now also as Linux Security Module), Medusa DS9. I'm testing grsecurity (and it's ACLs) now and I'm quite satisfied with it, but I wonder, what are pros and cons of other solutions. Anybody tried them and can share his experience with us?"