I really want one of the Reef Keeper Lite Basic Plus controllers because it can monitor pH, temp, and I think ORP (may need an addition). The only reason I give a crud about monitoring pH is because I want to hook up my calcium reactor, otherwise I wouldn't worry about it. The temperature is something I want monitored so I can run a chiller/heater combo and not worry about them competing against each other. ORP is something I'd like to monitor just for fun.
I wouldn't have a controller if I wasn't going to run a chiller or CaRX. It's just not worth the time/money to me for a regular tank.