I currently have a Milwaukee Instruments PH600AQ Ph Tester and it doesn't seem to work very well for me. It seems like I constantly have to calibrate it (like every week) Not to mention that it never comes close to my two other PH testers (one drip and one instant strip)
I'm willing to spend a little more and buy a good PH meter that I don't have to calibrate it constantly. (and something that I can trust)
I'm currently leaning toward the Hanna HI 98129 (PH and TDS) I do have a TDS meter now, but I wouldn't mind just having to use one tester.