Different opinion. I think they are useful from a gee wiz point of view or out of curiosity and one time is probably enough. Beyond that I do not believe they are ready yet. Similar to what we have seen with lighting over the years as MH slowly fades out and LED's become technically more efficient with regards to reef keeping and our knowledge with using them.
In my opinion it comes down to the product price point and the testing standards and methodology between tests. This to me is the deal breaker because I'm a standards guy and I do not see how they recalibrate the unit between tests. Every sample should be treated unique and the machine(s) should be recalibrated after each use. This is expensive which gets back to my product pricing or hobby grade tests vs. cancer research.
There are too many posts asking about the results, good, bad, what to do, high tin, high zinc, why, what caused, etc. In the end I think they are nothing more than a novelty at the moment until processes, proceedures, and work flows get worked out. And I've done two by ATI and have a 3rd coming tomorrow. I like ATI, I think they are professional, and kind. I've exchanged emails and the support is great, honest, and no sales pitch.
Lastly I'm also a data horder so a huge fan of bid data. This is one of thise pieces I think the reefing community could take advantage of as far as numbers go. But...it comes back to the quality of the results. Junky data, well, isn't going to do anything than lead us down a gopher hole and I for one do not want Bill Murry above ground with a rabbit made out of C4 dropping in my hole ruining my day
