I've been using this for over a year for everything in our startup, from lists of customers and prospective customers to lists of investors, advisors, and the like and I have enjoyed the simplicity. Compared to other CRMs this tool is much broader likely because it leverages a spreadsheet-like interface which makes it much more familiar, yet somehow it feels a lot easier to use. Other CRMs are only optimized for sales, but don't go broader to accommodate other use cases and that made them very unintuitive.
But aside from the basic features, hands down the best features are the network ones like the ability to map your network and see the strength of your connection and leverage it with the Alliances feature. By adding allies who can help you get intros to people in a secure and safe way (without exposing people's entire rolodexes) you can leverage their network and expand yours. I would highly recommend this to anyone running a startup who has to manage a number of different people and organizations in one place, it's been a lifesaver for us.