This is the primary use case of the Revenue Cycle modeler. If you set up your transitions in your model to fit the business processes, you can track conversion rate/velocity through the success path. So you could identify a transition between a contacted lead (let's call them a Sales Accepted Lead), and have it trigger the lead to move to the next stage (let's call it Sales Qualified Lead) when they change the lead status, or convert the lead to an account/opportunity. Then, you could use your Success Path Analyzer to see how many leads moved from SAL to SQL, the overall conversion rate, and the time spent in each stage.
The workflows function very similarly to how a smart campaign works, but you get to use all the fancy analyzers to visualize the movement between stages.
It's probably possible to do this through some custom fields and reports in SFDC too, but if you have the RCA activated, I'd recommend starting there.