Disclaimer - I have the TF-100 and use it regularly (used to use the Taylor similar kits) and have been testing my own pool for a long time and am very comfortable with it. A long time ago I used to periodically take samples to the local pool stores for check/comparison, but stopped that practice based on the large variability in results. Fast forward: today's pool stores seem to have shifted to computerized testing (I think Clear Care is a big name) which uses a very small water sample but I believe it "samples" the sample multiple times (10?) to arrive at results. Not sure what the analysis methodology is that it uses, but it does seem to be relatively consistent. I have the good fortune to be able to get my water tested just about as often as I want at a store and I've been comparing results to the TF 100. Pretty close. CYA and TA are very close, certainly within the testing method accuracy. Their Chlorine (TC and FC) tends to run a bit lower than the TF 100 results but only by 1-2 ppm for TC. pH is pretty close with the TF 100 test usually a bit lower than the store, but it's a subjective color comparison test so probably not worth mentioning.
So, question: Has pool store testing generally improved to the point that you can rely on the results? Everybody weigh in!