IMHO, no it's not worth it. The reason is because of the constant need to calibrate it. If your going to fuss with that all the time, you might as well save your money and just do a CA test.
I have one and have been using it for over four months now and have checked the calibration each month and it has been dead on... but i still test with a test kit, just incase
I love the saline monitor. Great for water changes and monitoring when you have several tanks, raising food, etc. I use it more than any other piece of equipment (except for monitor on reef)
FWIW, IMO your $ may be better spent on something other than a monitor of any sort. Personally I feel that a PH monitor is a great thing to have, and a PH controller great if you run a Ca reactor, but otherwise you might be better off upgrading something else (skimmer, lights, pumps......)