Hi Tammi.
For what it's worth, we've chosen to not roll out Resource Calendars. We have our standard calendar setup with our holiday exceptions and we find this good enough for now. We don't see quality return for the effort of taking this any further.
Calendar workday exceptions come into play during Autoschedule. While we're pretty heavy autoschedule users, we're also really good at Team/PM/RM communication. When a resource is going to be out for an extended period, all parties are well informed and we just handle this manually in the project schedules and with our brains.
Same kind of thing for "off hour" work. Example: we need a group of techs in a space during a base calendar non-workday (a Sunday, for instance). Although the project schedule may show the activity for Friday or Monday - the work still happens on Sunday because people communicate. When done, the resources can still enter their time in their timesheet to Sunday just fine. Clarity doesn't make work happen, Clarity doesn't stop work from happening. Clarity is a communication tool.
The project schedule is important, but Clarity doesn't mange projects, people do. I've joked that when I get beat up at the water cooler because project X went a week late because critical path resource Y was out for a week and THE SYSTEM didn't know this - then I'll train ya'll on managing those resource calendars to make THE SYSTEM know this. Of course, training does not guarantee execution...
I would roll out resource calendars if...
1) There was an easy way for the resource themselves to own this (have the option to stack this in with the Resource - Self (Auto) permission).
2) It was easy for a resource to set a date range ("I will be out on maternity leave from X to X").
3) There was some tie back with timesheets that makes "owed" timesheets disappear for the resource for the duration of the OOO.
4) Must have some kind of centralized "Out of Office" functionality/view. We use Exchange for this now. If there was an integration where the resource only had one action or Clarity's capability was so superior we could do away with the Exchange we would find value.
Technically they do what they're supposed to do. Functionally, we see rolling 'em out in any operational fashion more trouble than it's worth.