CRM project for SaaS companies

Hi Everyone,
We encode CRM system for Software as a services companies. Recently we have been doing CRM market research about SaaS companies who use CRM systems.
Is there any CRM system that you are using now? Which features do you like and don’t like in these systems or which parts you want to change?
If you have any pain while using your existing CRM system to improve our project, please share it with me.
Your opinions are very important for our CRM project. Thanks!