If you're on Google Apps, this is the CRM for you!
What do you like best?
I don't have to open up other tabs or go to a different place to view what's going on with any of my pipelines. It's especially good for sales/CRM but we also use it for hiring and support. One way to describe it is to say it's gmail tags on lots of steroids with some helpful tools (email snoozing and view tracking) built-in as well.
What do you dislike?
It's a bit pricey for what you get. If Call Logs and Meeting Notes were included in the Starter Plan that would be much better but as is you really have to pay $40 per user per month for core functionality. Which is pretty high considering other CRMs are much cheaper for full functionality.
Recommendations to others considering the product:
Do you need a tool to manage workflows or a tool to generate new leads...Streak does not generate new leads at all but it's the best at email workflow optimization.
What problems are you solving with the product? What benefits have you realized?
Email management, Sales, CRM. It's really just an operational tool to better organize email and communication between your company and your vendors and customers. It's like tags but much better than basic tagging. If you heavily rely on email for communication, you have multiple people on your team, and you like keeping organized, this is definitely the best tool out there...