Jenna Yuill: So far, we've built out (but have not released yet) logs when a reminder email is sent to the client and whenever the client logs in and views the project.

We're currently looking into building out additional client actions as well (such as when they marked a task as complete, for example). That said, we DID just release an enhancement to client tasks where we state who performed the action when (see below). It's not a full report but at least gives you the details on the task itself!