The calendar invite tool within each manually written or templated email was exceptionally helpful for our salespeople. The customer support we received was also exceptionally strong and responsive. We had immediate access to their product team so that we could offer feedback and make requests.
There seems to be a similar need for this type of support with customer service, but due to the limited integration options with multiple SFDC objects, we couldn't offer this outside of our sales org.
Calendaring integration across multiple tools, both Google for individual use (google calendar) and reporting/centralized data (SFDC).