I like that it's easy to use, has an excellent customer service team who are always willing/able help you with any questions or concerns about their product! It is expensive compared other options out there but if your looking at only one tool then this should be considered as well since they have great support staff available 24 hours 7 days per week via phone email chat live video etc..
The ability of being able to track all my contacts in 1 place makes life easier when trying new clients i'm working through them so having everything under ONE roof saves time!!