I have the calcium and alk test kits, and I had some trouble at first. The cuvets that come with the tester (2 each) have wildly inaccurate 10 ml marks, leading to incorrect results. After reading several threads here I started using a 10 ml syringe, and have been getting much better results. I double/triple checked everything with some Red Sea test kits and at the LFS, and everything seems fine. I really like using them, as I have trouble seeing the color change in the titration tests.
They also come with 20 or 25 sets of reagents, and refills are something like $12 for another 25.