Killer feature for me is being able to cmd+click on file paths in the terminal to open them. I use this constantly. There are plenty of other features too such as being able to reopen a tab you closed accidentally.

For a while it had a lot of features that Terminal.app was missing. Terminal.app has fixed a bunch of these things, but iTerm is still my preferred terminal app on macOS. iTerm has overflowing with features (though that doesn't necessarily mean that they are useful to you).