Marketo is not always super easy out of the box because many startups are following ad-hoc marketing practices. There's a fairly significant upfront investment in building out the logic/rules/process that will drive the system, but typically, it's getting agreement on the process vs. implementing the logic in the system that takes the time/effort.
I would recommend either getting some significant help with implementation (not just a few hours) or hiring an expert who has rolled out the system before. The system is extremely powerful, but many companies are still using it very basically (email blasts vs. nurturing, etc).
If you do it right, Marketo (along with the effective use of Salesforce) can help you drive a repeatable and consistent way to track marketing campaigns to ROI (Revenue Cycle Analytics, included in the Select edition is required). It can transform the conversation around marketing to focus on revenue vs. "brand awareness" or clicks and pageviews.