When my pool was built last year, I also had so many questions about getting accurate pool testing readings. I was very unsure if I could tell the difference between small shades of yellow, pink, orange, etc.... so, despite reading all the good advice here, I went and got myself many hundreds of dollar in test kits:
TF-100
ColorQ
Extech EX900 (
http://www.extech.com/instrument/produc ... ab_CL.html)
And of course a smattering of test strips, etc...
I got a bunch of buffer solution, and I use the extech for more of a reference testing for Free chlorine and pH. I was initially interested in ORP as well since I have an Autopilot TC system, but like Jason, I couldn't get ORP to work reliably, it's much easier to just set a % output on your SWG.
pH - was by far the hardest for me to get an accurate handle on. The Extech made it easy, but unless you have tons of buffer solution and time in order to calibrate, it's not practical for an everyday pool owner to use. The Color-Q was fairly reliable in testing pH, but it always read +0.1 to 0.2 higher than the actual pH. After several hundred tests now, I think I've got the basic phenol red test down to the point where I can discriminate slight changes in pH.
FC- It's very difficult for me to differentiate between various shades of yellow or pink. The FAS-DPD in the TF-100 is extremely accurate and reliable for testing FC. It correlates extremely well with my direct chlorine meter. Be sure that you use fresh reagents though. I noticed that my first set of reagents (stored improperly my fault) from last summer were no longer accurate. The Color-Q unfortunately is fairly useless in this regards for me. I want to keep my FC above 4 and more towards the 5 range. In this range, my colorQ always reads too high to measure.
ALK- ColorQ completely useless. It gives me very variable test results, and all of them are 30-40 points below my drop based test. Drop based test have always been very reliable for me. I must say that the dropper tip on my TF-100 gives drops that are slightly too big, I always read 10 points lower (1 drop less) compared to using the original taylor bottles/tips.
CH- ColorQ isn't too bad in this respect. I've had readings +/- 50 compared the the drop test. However, the drop test is so much more reliable (you get the same result each time). just watch the age of your reagents and make sure they are stored properly.
CYA - ColorQ is hard to assess. I always get a reading about 25-30 points lower than actual. Even following all the precautions - warming up the sample, mixing thoroughly, giving it time to dissolve, etc... ColorQ always gives a much lower reading than actual. I don't particularly like the turbidometric test with the disappearing dot either, but it seems to be more in the ballpark than the colorq.
In short, my ColorQ is basically only good for pH, and really only after I've used a very accurate pH meter to determine the difference between the ColorQ reading and the actual pH. It's ok for CH (at least in the ballpark), but overall probably not worth it.
The TF-100 is has been overall much more reliable and accurate. Just make sure you have fresh reagents. I still wish there was an easier way to discriminate small changes in pH (without a good pH meter and lots of reference buffer solution) there just isn't. Keep practicing with the phenol red drops. I have to hold it up to a blue sky in order to detect small differences. If I use a white background or even a cloudy day, I have trouble with the comparator. Luckily, once my Autopilot TC pH meter was properly calibrated, it's been providing me accurate and reliable readings, and I haven't had to recalibrate for at least the last 4 months.
And if anyone knows of a better and more reliable way to test CYA, let me know.