I've found these tools extremely useful to understand user behavior. We rely on Fullstory all the time to improve the user experience, to identify bugs, and to debug user issues.

The result of these tools is a far better user experience on our site and many other sites.

"recording every keystroke" makes it sound like there's malicious intent, but it's misleading. It should be added that all these tools have a lot of options to avoid tracking sensitive data (like password fields) and we always rely on that (in fact anything else would be a compliance violation for us).