Biggest problem is that it gives too much info all at once and also seems to give a lot of precision that just isn't there. If you don't know how much water your pool holds (and I don't mean to the nearest 100 gallons! then it is an estimate at best.
It also does not tell you step by step what to adjust first and some of the info on how pH is changed by added a certain chemical does not take into account pH rise from CO2 outgassing and the effect of different TA levels and whether there are non bicarbonate buffers present also. We have had people try to 'correct' for the pH effects of adding a chemical with (expected by us) disastrous results.
IT can be a useful tool in the hands of ewho understands pool water chemistry but for the average user it ir more likely to get you into trouble.