Corteza CRM to implement a custom CRM requirement

I am currently evaluating Corteza CRM as an option for a CRM related requirement for an ongoing small scale development project.Have any of you used this open source application and what are your opinion on this in terms of userbility and configurability. How ease is integrating custom changes if required?

I found an community forum but do they also offer a paid service to assist with configurations and customizations if required. I couldn't find this information when checking related resources on thier It would be great if you could point me to such a service offered by Corteza team or third party vendors as i need to expedite a customized prodduct development based on this CRM ?