RCA is an add on product that I believe comes with the select level pricing tier (don't quote me on that though). It expands the analytics already in Marketo with more of report builder and pivot-table based reporting system, along with a few analyzer. It's where you can, at least in theory, run reports to look at the performance of your programs, your revenue cycle, opportunities, and overall revenue influence.
The opinions on the tool range widely, and while I've had some success with the tool at past organizations, it ultimately was not a strong fit for us currently. Most of the reporting we would be looking at in Marketo we're instead doing via a combination of Salesforce reports, custom excel work, or data viz tools like Tableau. Marketo also has a slightly different view of the world than how Salesforce sees it, which limited its value to us from an executive-level reporting engine.
I think right now the interface for RCA feels really out of place with the rest of Marketo, and could use a serious user experience overhaul (not just a fresh coat of paint). Right now, it's just confusing to use. There's certainly potential there, and I plan to continue to have a look at it as the product evolves, but it's just not where we need it to be to find value at this time.
That said it really depends on your use case, I've met many users who've found value in it. If you do evaluate it, go into a demo with specific data problems or questions you want to solve. Get sample reports that clearly demonstrate how you could arrive at the analysis you need. All too often I've seen others (or done so myself) go down a rabbit hole of analytics without a clear destination in mind, and end up coming up with even more questions than when they started.
Hope this helps!
.png)