I like that they have so many different types of integrations, allowing us to connect our CRM platform in ways we couldn't do otherwise! It's very easy for me as an admin user - not sure about other users who may be less tech-savvy? The fact it is cloud software means there are no servers or physical hardware required which makes this tool great value compared against competitors (at least from what i can tell).
We've been able use appointmentscore since before infusiionsloft was released officially by Salesforce but now everything has just got easier!! Scheduling meetings/appointments around clients' availability & timeslots using google calander etc all at once without having multiple tabs open each time would drive you mad. Easy access via website too if needed when away form computer / phone.