Richard,
for us it's been trial by fire. We've set goals around trying to move key reports into RCE and while there is a learning curve, it's pretty fast. It's been a great forcing function for us to get more out of Marketo, scale/centralize our reporting, and find areas of improvement within our Marketo management (e.g. campaign tagging).
I will add that RCE is far from perfect - there are certainly limitations to it that we still need to build out in Excel. I find that it's light in Opportunity analysis (many metrics are only available at lead level) and there is nothing on the user level (e.g. difficult to segment by team, such as inside vs. outside reps).
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