Depends on what you mean by deployment. We use puppet for managing our os, packages and basic file structure. We use home-grown bash scripts for deploying new versions of applications.

For keeping track of os-level packages and the like, I find Puppet much better than something I could build myself. It doesn't just take care of the initial setup, but also handles incremental changes. And it does so in a largely declarative language. It all guarantees that the entire installation is documented and replicable.