I don't like the chemical test kits either, they've possibly caused the death of 1 of my fish already. I find that the colours are hard to distinguish at the best of times. For instance, the light in one room makes the ph test appear to be 0.2 higher than another room. The readings of them all look different if I check them next to the tank (due to the tube lights), next to the window (natural light), at different times of the day (due to the mix of room/natual light). Because of this I thought my Nitrite was 0.2 so I perfored a 10% water change. A few hours later a guppy had died, the lfs tested the water and said it was 0.3. (Did they say this just to invalidate their guarantee of replacement, or was it my difficulty of reading tests.)
I'm considering buying an expensive electronic ph tester but not sure about the other tests. I've heard you can get electronic nitrite and nitrate testers but have never seen any. Has anyone used one?