We are just getting into the specifics for WF Planning.
Our plan is to use a mix of both planning and core/workflow for our organization.
Planning will be used primarily to capture our global taxonomy and high level details, then core will be used to execute on a more granular level - pulling details from the global records into more bite-sized campaign projects and workflows. One con we've had along the way is having to untangle processes that are currently happening outside the system in excel and figuring out how to document that process and move it to planning. Secondly, we are attempting to figure out how to scale the solution across multiple departments and execution channels, due to lots of nuanced ways of working.
It's crucial for us to get everyone STARTING in planning, and then kicking over details from planning to workfront core for execution. We're getting there, but not quite 100% yet. We have HIGH HOPES!