Another way to think about reusing your rules is to realize that your rules need to be attached to spaces (more or less). So, if you copy the spaces, the rules go with them. If you have a recipe you like for a simple flow, you could make that into a template that could then be applied whenever anybody uses the Space Wizard to create a new space.
Rules themselves have both context and parameters which are difficult to reuse. By providing much of that context in the template approach, you solve one part of the problem. Each rule still has to be re-parameterized, i.e., any mail recipients changed, workflow swimlane assignees changed, etc.
