I actually really like it. You can track emails, you can send later. You can create 'snipets' so that you have a standard email saved for each domain.
Also, If you find 10 contacts for one of your domains, you can 'mail merge' so that each contact receives a personalized version of the same email. I don't spam, but I do like the 'mail merge' feature for a small group.
The videos on streak.com are pretty straightforward. I think I watched one and then played around with it from there.
I have had some random issues with the mail tracking though. Like people would open my emails and respond to me without me ever getting a notification that they opened the email. (Actually, in hindsight that may not have been streak's fault, I believe some people block mail tracking)