The best part of HubSpot CRM is its price...free! It makes a good solution for someone needing just a simple, cost-effective way to manage contact relationships. I also like the integration with Outlook, although it could use some improvements. It makes it easy to add new contacts right from your Inbox. The desktop app updates you every time a contact has opened your message, without relying on "read receipt" requests.
The Outlook integration is often buggy and either crashes or fails to update. It causes Outlook to lag considerably, resulting in a permanent plug-in performance warning from Outlook. The desktop notification is handy, but pings every time someone opens an e-mail you tracked, not just the first time. This has resulted in ping after ping after ping as the recipient scrolls back and forth between e-mails in their inbox. It's annoying, and cannot be "turned off" for an e-mail after it's been sent. The tracking is also embedded deep in an e-mail, so any replies and forwards get the tracking added automatically, making it difficult to know which e-mail in a series has actually been opened.
I recommend HubSpot CRM for anyone looking for a low-cost (free) solution, especially if you're still using spreadsheets or scraps of paper to keep track of contacts.
HubSpot CRM has made it possible to keep track of leads, customers, vendors, etc. It's been easier to manage our relationships now that we're not using spreadsheets and sticky notes to keep track of important contact information.