Our team at https://gridle.io, uses 2 forms of calendar precisely for almost all the reasons stated above.
https://calendly.com : God, this is great for sales & support teams to set up calls with our customers. Reduces atleast 3 emails to figure out a mutually convenient time to set that up.
https://calendar.google.com : This is our Gantt chart, Excel-Sheet, Deliverables, Product Roadmap and To-do list.
We’ve integrated both these tools with Gridle as well. Srinivas Rao : We’d like to educate our users about this. Any chance we could do an interview? Do let us know.