We have been using Process Builder instead of workflow for many years now. But we have been bitten a few times by problems with Scheduled Actions in PB.
Specifically, we were just bitten by the behavior described here https://developer.salesforce.com/forums/?id=906F0000000fz6b and in several threads here on SE.
tl;dr: although this isn't clearly stated in SF docs, it appears that if a Process has Scheduled Actions already in the queue, and you make and activate a new version of the Process, not only do those actions stay in the queue, but changes to the triggering record will no longer cause them to re-evaluate. That can lead to emails going out that you don't want, if a new version has been activated since the action triggered.
There doesn't seem to be a great way to avoid this, at least not without a ton of extra work to clear out the queue and then re-trigger the Scheduled Action after each new version change.
We are thinking of making a new policy of using Workflow for all Scheduled Actions where we don't want to write code, and continuing to use PB for other uses.
Question: anyone else doing it this way? Sounds like a good idea or a bad idea? General feedback and did-you-think-of-this welcomed!