The integration of many services is very easy, I am using it to integrate different social media platforms such as Facebook Messenger bot/app which can send messages via chatbot within my website pages or in messenger itself that makes things easier than before; however there are other few integrations where you have difficulty integrating them at first but then after some research everything becomes much clearer & user friendly! It's difficult sometimes if your knowledge base isn't enough when implementing this system so make sure yours skillset covers all aspects needed like business domain etc..
As an online marketer i use their API features mainly e-mail marketing automation tools especially mailchimp (also available through petium) - they also do ATS tracking / CRM analytics from data sent by email campaigns.