[Brian]

OmniFocus will sync the entire contents of your database to all the machines, but that doesn't mean that you have to look at all of them in both places. :-)

The way I keep work and home tasks separate is through perspectives; on my work machine, my perspectives are all focused on my "Omni" folder and the projects it contains. Similarly, at home, they're all focused on the "Personal" folder/projects.

To focus on a set of projects, select them in the sidebar, then choose Focus On from the View menu. Context view in that window will now only show actions from those projects.