It is the best available solution for small businesses due to the licensing model and the ease of use. For companies like us who implement this for customers, it is easy to implement and train users. Larger companies would prefer to use existing products that have been developed for their specific industry or department.
Probably the most important aspect would be the licensing model which makes it affordable for all businesses. Can be adapted to the business without having to change the business model around the CRM product.
It really filled a gap in the market where small business could not afford expensive CRM solutions.
As we are implementing this as a solutions for our customers we don't pay for it, but it provides a monthly income from supporting the infrastructure this has been deployed on.