To be honest, I do look at the temp gauge but very ocassionally. I would bet that most operators look at the temp gauge as the very first course of action once they notice steam or anti freeze spouting forth. My advice is save your money and get in the habit of cleaning the screen often. The addition of a temp gauge won't stop the machine from whistling at you.
Hmmm, that sounds kind of heavy handed, that's not me.
Should you decide on adding a guage, may I suggest the type that has a "bulb" on the sensor end. Pretty much a thermometer in construction. It requires no electrical connection to operate and thusly simplifies installation and is inherently reliable due to reduction of working parts. I added one on my air cooled motorcycle, no complaints.
All the best, post us some pics please if you go with one.
Martin