I like it. I appreciate being able to do things like monitor my system temperature, although lately I just keep Activity Monitor open all the time for the rest. The only really bad thing isn’t the poorly worded interface, the system resources being used to monitor things that aren’t being displayed, or even the need for an external tool—it’s the checking in with the dev. If my network connection isn’t established by the System Monitor has loaded, it turns off the additional tool AND deactivates my choice—neither of these makes any sense or has any necessity. I then have to open the preferences and reactivate everything. Not good. That and the semi-aggressive update notifications about updating to support machines I don’t have.
Thanks for your feedback. Most things you mention don't actually fit with the app, however.System Monitor never consumes resources for items it doesn't show. The external tool is NOT needed. It is an optional add-on if you like to utilize advanced features which are no longer permitted in the App Store. Although the App Store may sometimes need a network to validate your license with Apple, the app itself NEVER requires an Internet connection unless you explicitly enable features that would enforce this, like showing your WAN addresses. There are also no notifications or any "check-ins" unless you expressly request to be informed about updates of the optional add-on.