In every version of Sonar before X1, there was a visible display of what recording mode you were in: sound on sound, overwrite, or autopunch. With X1 this feature was discarded. We can easily see if we're in autopunch, but no display for overwrite, sound on sound, or comping.
The only way to know is to open preferences and look under Project/recording. When you change the record mode you can't start the transport and leave preference open, so you can see the mode. You have to close preferences and then if you forget which mode you're in you have to stop the transport and reopen preferences to look.
It sure would be nice if we could add more things to the custom module of the control bar. We're limited to only buttons, no displays like sound on sound. With all the great new features we're getting, it seems this would be a great nuts and bolts basic feature that would be useful to many.