Is SysInspector useful? For some yes, for others no. Do you think Grandma will know what to do with something like this
(picture on the right)?
She might mess around and finally delete it (and it could be a necessary file), or ignore it because she doesn't know what to do (and it could be a malicious file).
But for others, it can be a wonderful center for data they need or want. I know that I have found the "Important Registry Entries" section informing, and "System Information" provides nice exact details on the computer's specifications.
So SI is not for the average user, but for others it can be a jewel.